Preheat a grill to medium. Grill the bell pepper until tender, about 8 minutes. Remove from the heat, let cool, then thinly slice.
Top one half of the tortilla with the pepper and two cheeses and fold to make a half-moon, pressing down firmly. Place on the grill and cook until the cheese starts to melt, about 2 minutes. Flip and cook on the other side until the tortilla is warmed through and the cheese is melted, 2 to 3 minutes. Let cool, then cut into triangles to serve. For peoples portions, serve with the salsa and sour cream on the side.