How to Make It
Preheat oven to 425°F. Heat oil in a large skillet over medium-high. Whisk in flour, and cook, whisking constantly, until light brown, about 2 minutes. Whisk in chili powder, tomato paste, cumin, garlic powder, and salt. Cook, whisking constantly, until fragrant, about 30 seconds. Gradually whisk in broth until smooth. Bring to a boil, stirring often, until sauce is thick enough to coat the back of a spoon, about 2 minutes. Remove from heat; let cool 5 minutes.
Spread 1/2 cup sauce in bottom of a 13- x 9-inch baking dish.
Dip each tortilla in sauce, letting excess drip off. Place 1/4 cup shredded cheese in center of each dipped tortilla, and roll up. Place seam side down in baking dish. Drizzle with remaining sauce. Sprinkle top with remaining 3/4 cup shredded cheese.
Bake in preheated oven until sauce begins to bubble and cheese melts, about 12 to 15 minutes. Top with onion slices, and drizzle with crema.