Preheat oven to 350°F (175°C).
In a large skillet, cook ground beef and onions over medium heat until beef is browned. Drain excess fat.
Add garlic, chili powder, cumin, salt, and pepper. Cook for another minute until fragrant.
Stir in chili beans and tomato sauce. Simmer for 10-15 minutes, stirring occasionally.
In a 9x13 baking dish, layer half of the Fritos, followed by half of the chili mixture and half of the shredded cheese.
Repeat the layers: Fritos, chili, cheese.
Bake uncovered for 15-20 minutes or until the cheese is melted and bubbly.
Remove from oven and let rest for 5 minutes. Top with sour cream, green onions, or jalapeños if desired. Serve warm.