In a medium bowl, add one can of rinsed and drained black beans, then mash half of them with a fork until slightly chunky. Stir in ground cumin, chili powder, garlic powder, and a pinch of salt and pepper. Mix until combined.

Butter one side of each slice of sourdough with softened butter. On the unbuttered side of two slices, spread the black bean mixture. Top with shredded cheddar cheese, then place the remaining slices of bread on top, buttered sides facing out.

Heat a large skillet over medium heat. Place the assembled sandwiches in the skillet and cook for 3 to 5 minutes, pressing down gently with a spatula. Flip and cook for an additional 3 to 5 minutes until golden brown and cheese is melted.

Remove the sandwiches from the skillet and let them rest for about 1 minute. Cut in half and serve warm.