Step 1

Place the lentils in a medium saucepan and cover with water. Bring to a boil. Add 1 teaspoon salt. Reduce the heat to low and simmer until tender, about 30 minutes. Drain.

Step 2

Heat the olive oil in a large skillet over medium heat. Add the onion and bell pepper and saute until the onions are translucent and the pepper is tender, 7 to 8 minutes. Add the garlic and green chiles and cook about 1 more minute. Stir in the tomato sauce, ketchup, Dijon, brown sugar, Worcestershire, chili powder, vinegar, celery seed, black pepper, remaining 1/2 teaspoon salt and 1/2 cup water. Mix well, then add the lentils. Reduce the heat to low; cover and simmer, stirring occasionally, about 15 minutes.

Step 3

Butter both sides of the hamburger buns. Toast on a hot cast-iron griddle or skillet until lightly browned, 2 to 3 minutes.

Step 4

Serve sloppy joes on toasted buns, topped with sliced avocado and pickles on the side.