Preheat oven to 400°F (200°C). Heat oil in a large skillet over medium-high, then crumble in the beef. Cook, breaking it up, until browned and no pink remains, 6 to 8 minutes. Drain fat.

Stir in taco seasoning and the tomatoes with their juices. Simmer until thickened, about 3 minutes, then remove from heat.

Arrange 4 tortillas in a single layer on a rimmed 10×15 inch sheet pan. Spread half the beef mixture over the tortillas and sprinkle with 1 cup cheese. Repeat with remaining tortillas, beef, and cheese.

Bake on the center rack for 12 to 15 minutes, until the cheese is melted and the edges are golden and crisp.

Cool 2 minutes, then top with sour cream, avocado, cilantro, and salsa. Cut into squares or wedges and serve.