Add onions, garlic, jalapeno, and cumin; season with salt and pepper.
Cook stirring occasionally until golden, 10-12 minutes.
Add tomato paste and cook, stirring, 1 minute.
Add beans and 1-1/2 cups water; bring to a boil.
Reduce heat to medium and simmer stirring occasionally until thickened, 10-12 minutes.
Add corn; cook to heat through, 2-3 minutes.
Remove from heat; stir in scallions.
Heat tortillas according to package instructions.
Fill with rice, bean mixture, and cheese (assembly instructions below).
Serve immediately with salsa and sour cream, if using, or freeze-wrap-freeze (see above) up to 3 months.
(Reheating instructions below).
To Assemble:.
Mound 1/4 cup rice, 3/4 cup bean mixture, and 1/4 cup cheese on one side of tortilla, leaving about 1/2 inch between filling and edge of tortilla.
Fold sides in and hold.
Starting from filled end, holding sides in as you work, tightly roll into a bundle.
Place on a baking sheet, seam side down, and prepare remaining burritos.
Reheating From Frozen:.
Microwave and oven: Remove frozen burritos from plastic wrap.
Place on a microwave-safe plate; microwave on high for 3 minutes.
Transfer to baking sheet; bake at 450 degrees until crispy, about 10 minutes.
This is our favorite quick method.
Microwave only: Remove frozen burritos from plastic wrap.
Place on a microwave-safe plate, covered with a microwave-safe bowl, and defrost at high power for 3-4 minutes; uncover, and microwave on high 3-4 minutes longer.
Oven only: Remove frozen burritos from plastic wrap; rewrap individually in aluminum foil.
Place on a baking sheet; bake at 450 degrees for 40 minutes.
Remove foil and bake to crisp, 5-10 minutes.
(To reheat defrosted burritos, remove any wrapping and bake for 10 minutes.