BBQ Tempeh with Avocado

-8 oz. tempeh, cubed

-1/2 large onion, diced

-1/2 bell pepper, diced

-1 1/2 Tbsp. olive oil

-1 heaping Tbsp. tomato paste

-1/2 cup BBQ sauce

-1/2 cup broth or water

-1/3 cup cilantro

-Salt and pepper,

-4 hamburger buns

-1 avocado, sliced and sprinkled with salt