Start by dicing the yellow onion, red bell pepper, and roma tomatoes. Mince the garlic and slice the jalapeños if desired. Rinse the canned black beans under cold water and drain them well.
In a large skillet over medium heat, add a splash of water or vegetable broth. Once hot, add the diced onion and sauté for about 2-3 minutes until translucent. Then add the red bell pepper, jalapeños, and garlic, cooking for another 3-4 minutes until tender.
Stir in the rinsed black beans and salsa, mixing well. Sprinkle the taco seasoning over the mixture and stir it in. Cook for about 5 minutes to let flavors meld.
Add the diced roma tomatoes and fresh cilantro into the skillet. Stir gently to combine and heat through for an additional 2 minutes. Taste and adjust seasoning if necessary.
Lay a tortilla flat on your work surface. Spoon a generous amount of the black bean mixture in the center. If using rice, add that too! Fold in the sides of the tortilla and roll it from the bottom up, wrapping tightly. Repeat with remaining tortillas.
Slice the avocado in half, remove the pit, and scoop out the flesh. In a small bowl, mash the avocado with lime juice, diced onion, diced roma tomato, and salt. Serve this delicious avocado mash alongside the burritos.