Preheat the oven to 350 degrees F (175 degrees C).

Combine chili and enchilada sauce in a small saucepan over medium-low heat. Bring to a simmer, stirring occasionally. Set aside.

Meanwhile, heat vegetable oil and chili powder in a small skillet over medium heat. Fry one tortilla until it starts to puff. Remove with a spatula and place on a plate. Immediately sprinkle about 1/4 cup cheese and 1 tablespoon onion down center of tortilla. Roll tortilla tightly around mixture and transfer, seam-side down, to a 9x13-inch baking dish. Repeat with remaining tortillas.

Sprinkle about 2/3 of remaining cheese over rolled enchiladas. Pour warm chili mixture evenly over enchiladas. Scatter remaining cheese over chili mixture.

Bake in the preheated oven until the cheese is bubbling, 20 to 25 minutes.