Preheat oven to 350. Line a 9x13 baking dish with corn tortillas (12-15 tortillas). Make sure to go up the sides of the pan with the tortillas.
Brown ground beef and drain it. Drain and rinse both cans of beans. Do not drain the tomatoes. Return ground beef to the hot skillet. Add the tomatoes, taco seasoning,water and drained and rinsed beans to the ground beef. Continue cooking until the taco seasoning is dissolved.
Add the meat and bean mixture to the pan lined with your tortillas. Top with the shredded cheddar and pepper jack cheeses. Bake until cheese is melted and tortillas are crispy on the edges.