Start by washing and chopping all your vegetables. Thinly slice the red onion, dice the yellow onion, and the bell peppers, and finely chop the jalapeño. Mince the garlic and zest the lime.
In a large skillet, heat the olive oil over medium heat. Add the diced yellow onion and cook until it becomes translucent, about 3-4 minutes. Then add the minced garlic and sauté for an additional minute until fragrant.
Stir in the red and green bell peppers along with the jalapeño. Cook for about 5 minutes until the peppers have softened. Sprinkle in the dried oregano, chili powder, sugar, and a pinch of kosher salt. Stir well to combine all the flavors.
Add the rinsed black beans and diced tomatoes (with their juices) to the skillet. Stir well and cook for another 5-7 minutes until everything is heated through. Taste and adjust seasoning if necessary.
While the skillet mixture is cooking, prepare the lime yogurt. In a small bowl, combine the plain Greek yogurt or sour cream with the zest and juice of 1 lime and a pinch of kosher salt. Mix well and set aside.
Once the black bean mixture is cooked to perfection, serve it hot. Top with a dollop of lime yogurt, sliced avocado, and fresh cilantro leaves for an extra burst of flavor.