Sloppy Lentils

This was an awesome recipe - so much better than the last sloppy lentil recipe I tried: http://www.passionatehomemaking.com/2008/05/f-n-sloppy-lentils.html

I changed it up a bit and I doubled the recipe for two families. Here is my revised version for the single recipe with my revisions in red:
3 cups water
1 cup lentils, rinsed
salt to taste
1 cup chopped onion
1 chopped green pepper
3 tablespoons olive oil
15 oz can diced tomatoes
1/2-1 (6 ounce) can tomato paste (omitted)
2 cloves garlic, minced
1/2 cup ketchup
1 teaspoon mustard powder (I used prepared mustard b/c I didn't have the powder)
1 tablespoon chili powder
3-5 tablespoons rapadura, molasses, or honey (I used honey)
1 Tbsp white vinegar
salt and ground black pepper to taste
4 hamburger buns, split
Combine water and lentils in a saucepan; season to taste with salt if desired. Bring to a boil over high heat, then reduce heat to medium-low, cover, and simmer until tender, about 30 minutes, stirring occasionally.
Meanwhile, cook onions with the olive oil in a large skillet over medium heat until the onions have softened and turned translucent, about 4 minutes. Add tomatoes, garlic, tomato paste, ketchup, mustard powder, chili powder, molasses/sweetener, vinegar, salt and pepper; blend roughly with an immersion blender simmer 5 to 10 minutes until thickened (I added it to the lentils first and then simmered)
Drain lentils and reserve cooking liquid. Stir lentils into sauce mixture, adding cooking liquid or water as needed to obtain the desired “sloppy joe” consistency. Serve on buns.
I served this with the rolls that are a few posts down.