Ultimate Lentil French Onion Soup Recipe

Sometimes you crave that rich, savory depth of a bistro classic but need something with a bit more staying power for a weeknight meal. This Lentil French Onion Soup bridges the gap perfectly, offering the caramelized sweetness you love with a hearty boost of plant-based protein.

It has quickly become my favorite way to warm up on a damp evening, filling the kitchen with the most incredible savory aroma.

What Makes This Lentil French Onion Soup a Keeper

The magic lies in the slow-cooked onions, which transform into a sweet, golden base that melts into the broth. It feels incredibly indulgent, yet it is packed with fiber and nutrients thanks to the addition of tender green lentils.

I love how this recipe satisfies that deep craving for comfort food without feeling heavy or greasy.

Plus, it freezes beautifully, meaning you can double the batch and save some for those busy nights when cooking feels impossible.

If this dish hit the spot, you’ll want to try my Cozy New Year Noodle Soup Recipe next, plus the Hearty Zucchini Fritters Recipe delivers the same bold flavors.

Everything You Need for Perfect Lentil French Onion Soup

Here is the simple list of ingredients you will need to gather:

• Yellow Onions: Large sweet or yellow onions work best for caramelizing.
• Butter: Adds a rich, creamy flavor to the cooking process.
• Olive Oil: Prevents the butter from burning during the long sauté.
• Garlic: Fresh cloves add a necessary punch of savory aromatics.
• All-Purpose Flour: Helps to slightly thicken the soup body.
• Vegetable Broth: Use a high-quality broth for the best base flavor.
• Apple Cider Vinegar: A splash provides the acidity usually coming from wine.
• Balsamic Vinegar: deepened the color and adds a complex sweetness.
• Italian Seasoning: A blend of herbs that complements the earthiness.
• Green Lentils: These hold their shape well during simmering.
• Gruyere Cheese: Melts perfectly for that classic cheesy top layer.
• French Baguette: Essential for the crispy, toasted crouton topping.

My Method for Perfect Lentil French Onion Soup

Let’s get cooking with these simple steps:

1. Start by preparing your onions, as they are the star of the show here. Slice the tops and bottoms off your onions, remove the papery skins, and cut them in half from root to tip. Slice each half into thin, uniform half-moons so they cook down evenly.
2. Place a large, heavy-bottomed pot or Dutch oven over medium heat and melt the butter with the olive oil. Toss in your sliced onions and settle in for the most important part of the process: caramelization. Cook them for about 40 to 45 minutes, stirring occasionally, until they turn a deep, golden brown and smell sweet; if you want an even deeper flavor, you can go a bit longer, but watch carefully so they don’t burn.
3. Once the onions are jammy and soft, sprinkle in the salt, flour, and minced garlic. Stir this mixture constantly for about two minutes to cook off the raw flour taste and release the fragrance of the garlic.
4. Pour in the vegetable broth, the apple cider vinegar (in place of wine), balsamic vinegar, Italian seasoning, and the dried green lentils. Increase the heat to bring the liquid to a rolling boil, then cover the pot and reduce the heat to low. Let the soup simmer gently for 20 to 25 minutes, checking occasionally, until the lentils are tender but still have a slight bite.
5. While the Lentil French Onion Soup is simmering, preheat your oven broiler and prepare the toppings. Slice your baguette into rounds, place them on a baking sheet, and pile a generous amount of shredded Gruyere cheese on each slice. Broil them for 1 to 2 minutes, watching closely, until the cheese is bubbly, golden, and gooey.
6. Ladle the hot soup into bowls and immediately top each one with a cheesy, toasted baguette slice. Serve immediately while the bread is crisp and the cheese is stretching.

My Best Tips for Perfect Lentil French Onion Soup

Don’t rush the onions; letting them cook slowly is the secret to getting that deep, rich flavor in your Lentil French Onion Soup.

I recommend using green or brown lentils because they hold their shape well and add a lovely texture without turning to mush.

If you prefer a thicker broth, you can mash a small portion of the cooked lentils against the side of the pot before serving.

How to Serve This Lentil French Onion Soup

This soup is hearty enough to stand on its own, especially with those cheesy, toasted baguette slices floating on top.

I like to pair this Lentil French Onion Soup with a crisp green salad tossed in a vinaigrette to cut through the richness.

Make sure to follow me on Pinterest for more cozy comfort food recipes and easy weeknight dinner inspiration that the whole family will enjoy.

Lentil French Onion Soup

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• Author: Amelia Bryan
• Total Time: 1 hr 35 min
• Yield: 6 servings
• Diet: Vegetarian

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Description

A hearty vegetarian twist on the classic bistro soup, featuring caramelized onions and tender green lentils topped with cheesy toasted baguette.

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Ingredients

• 1 cup dried green lentils, rinsed
• 4 large yellow onions, thinly sliced
• 2 tablespoons unsalted butter
• 2 tablespoons olive oil
• 2 cloves garlic, minced
• 2 tablespoons all-purpose flour
• 6 cups vegetable broth
• 1/2 cup vegetable broth + 1 tsp apple cider vinegar (wine substitute)
• 1 tablespoon balsamic vinegar
• 1 tablespoon Italian seasoning
• 10 slices French baguette
• 1 cup Gruyere cheese, shredded
• Salt and pepper to taste

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Instructions

1. Slice the onions into thin half-moons after removing skins and ends.
2. Heat butter and olive oil in a large pot over medium heat, then add onions and cook for 40-45 minutes until deeply caramelized and golden brown.
3. Stir in garlic and flour, cooking for 2 minutes while stirring constantly to coat the onions.
4. Add the 6 cups of broth, the broth/vinegar mixture, balsamic vinegar, Italian seasoning, and dried lentils to the pot.
5. Bring the mixture to a boil, then cover and reduce heat to low, simmering for 20-25 minutes until lentils are tender.
6. While soup simmers, place baguette slices on a baking sheet, top with shredded Gruyere, and broil for 1-2 minutes until golden and bubbly.
7. Ladle soup into bowls and top with the cheesy bread before serving.

Notes

Green or French lentils work best as they hold their shape. Traditional wine has been replaced with broth and vinegar for acidity.

• Prep Time: 20 min
• Resting Time: 5 min
• Cook Time: 1 hr 15 min
• Category: Soup
• Method: Stovetop
• Cuisine: French-Inspired

Nutrition

• Serving Size: 1 bowl with toast
• Calories: 340
• Sugar: 8g
• Sodium: 850mg
• Fat: 14g
• Saturated Fat: 6g
• Unsaturated Fat: 7g
• Trans Fat: 0g
• Carbohydrates: 42g
• Fiber: 9g
• Protein: 16g
• Cholesterol: 25mg

Keywords: Lentil French Onion Soup, vegetarian french onion soup, healthy soup recipe, lentil recipes