Heat the olive oil in a large, heavy pot over medium heat. Add the onions and cook for 3-4 minutes until they’re translucent and start to soften, stir frequently.
Next, add the garlic, chili powder, cumin, black pepper and crushed red pepper flakes (if using); cook for 30 seconds to 1 minute, stirring frequently.
Add the chopped tomatoes, lentils, chicken broth and the bay leaves to the pot. Stir well.
Raise the heat to high and bring the broth to a boil. Lower the heat to medium-low, cover and simmer the lentils for 25 minutes or until almost tender. Stir occasionally.
Add the red and black beans and corn to the lentils, stir well to combine. Continue cooking, covered, on medium-low heat, for 15-20 minutes to let the flavors to come together and to get the lentils very tender. Stir the chili occasionally to keep from sticking to the bottom of the pot.
Find the bay leaves, remove and discard.
Taste the lentils and add salt if needed. Also, keep in mind the toppings you’re serving before adding extra salt. For example, if your toppings are salty like cheese or chips then factor that in when deciding. As a reference we didn’t add any extra salt to ours.
Serve the lentil chili with your choice of toppings!