Stem, seed, and cut red bell pepper into 1/2" dice. Halve grape tomatoes. Trim and thinly slice green onions on an angle. Drain and rinse black beans in wire-mesh strainer. Avocado will be prepped in a later step to help preserve its vibrant color.

Warm a medium non-stick pan over medium-high heat. Add 2 tsp. olive oil, peppers, half the green onions (reserve remaining for garnish), corn, and 1/2 tsp. salt to hot pan and cook 4 minutes, or until peppers begin to soften. Transfer to a plate and set aside. Reserve pan (no need to wipe clean).

Return pan from corn and peppers to medium heat and add black beans, 1/2 tsp. salt, half the grape tomatoes, and 1/3 the enchilada sauce to hot pan. Cook 4-5 minutes, or until beans are warmed through and sauce begins to thicken. Remove from heat and, using a potato masher or fork, coarsely mash beans until mixture forms a chunky paste. Some whole beans and chunks may remain.

Place two tortillas on prepared baking sheet and top each with 1 Tbsp. enchilada sauce, 1/4 the black bean mixture, 1/4 the pepper-corn mixture, and lightly sprinkle with shredded cheese. Cover each stack with a second tortilla and repeat layers. Cover each stack with a third tortilla, 1 Tbsp. enchilada sauce, and remaining cheese.

Bake tortilla stacks 14-18 minutes, or until cheese is browned. Meanwhile, wipe pan clean from making beans, return to medium heat, and combine remaining enchilada sauce and 1/4 cup water. Cook 3-5 minutes, stirring occasionally, or until warmed through. Halve avocado and remove pit by carefully tapping pit with the blade of your knife so it sticks. Gently twist knife to release pit. Scoop out the flesh with a spoon. Cut into 1/4" slices.

Drizzle remaining enchilada sauce on a plate. Use a spatula to carefully transfer hacienda stacks onto sauce. Top each stack with sliced avocado, sour cream, remaining tomatoes, and remaining green onions.