Soak 2 cups dry green or brown lentils in a large bowl covering them with cold tap water. Let stand for 2 to 3 hours.
In a large pot with a lid, heat 3 tablespoons oil and sweat ½ cup finely chopped onion, ½ finely chopped small red pepper and ½ cup finely chopped celery stalks on low heat. You want to let them soften and release liquid (sweat), but not let them brown.
Add ½ teaspoon salt and ⅛ teaspoon of freshly ground black pepper, ½ cup finely chopped carrot and 2 cups of broth. Cook, partially covered, for 10 minutes over low heat.
Add 1 more cup of broth, the soaked but drained lentils, and 1 ½ cups canned tomatoes and simmer, covered, for 30 minutes.
In a small skillet, while the pot is simmering, cook 4 ounces bacon strips for 2 or 3 minutes until they are a little brown and have released some fat.
Drain and add them to the pot together with 2 teaspoons smoked paprika. Stir to mix and continue cooking.
Keep on simmering, checking seasonings (be careful with the salt as the broth concentrates and can be salty), and adding more broth if you feel it's necessary. The amount depends on the type of lentils you use and how much the soaking process softened them. Check to see if the lentils are fully cooked and tender, and adjust the simmering time until the bite is to your liking.
Ladle the stew into bowls, sprinkle with chopped fresh herbs like parsley or cilantro, and serve with crusty bread.
Or better yet, refrigerate until the next day, and reheat before eating it. The flavors will be amalgamated and richer.