1. Preheat the oven to 300 degrees F.
2. Peel the onion, and chop it into small pieces.
3. Drain the liquid from the cooked (or drain and rinse canned) kidney beans.
4. Mix the rice, chopped onion, and beans in a bowl.
5. Put each tortilla on a flat surface.
6. Put 1/2 cup of the rice and bean mix in the middle of each tortilla.
7. Fold the sides of the tortilla to hold the rice and beans.
8. Put each filled tortilla (burrito) in the baking pan.
9. Bake for 15 minutes.
10. While the burritos are baking, grate 1/2 cup cheese.
11. Pour the salsa over the baked burritos. Add cheese.
12. Serve the burritos warm.