To make the chili sauce, in a medium saucepan over high heat, combine the guajillo chili and chile de arbol with the water. Bring it to a boil and then reduce the heat and let simmer for 15 minutes. Remove from the heat and let stand for another 10 minutes.

Put the chilis and the liquid in a blender or food processor and process until smooth. Strain the mixture through a fine-meshed sieve into a bowl, pressing on the solids with the back of a spoon to remove as much liquid as possible. Discard the solids.

To season the tortillas, dip each tortilla into the chili sauce and then let the excess run off into the bowl. Stack the dipped tortillas on a plate. Cover the stack with a plate or plastic wrap and refrigerate.

To make the filling, in a large skillet over medium heat, heat the oil until it shimmers. Add the onion, tomato, and garlic. Cook, stirring occasionally, until the onion is soft and translucent but not browned, about 3 minutes.

Add the squash, corn, tomato sauce, stock, Texas-Mexican Holy Trinity, and salt. Cook over medium heat until the squash is tender, about 10 minutes. Drain in a colander, discarding the liquid.

When you are ready to make the enchiladas, soften the tortillas. Heat the cup of vegetable oil in a medium skillet until it shimmers, about 375°F (190°C). Using a nonstick spatula, slide one tortilla at a time into the oil. Let it cook for 2 to 3 seconds, then turn it over and let it cook for 1 to 2 seconds more; the tortillas should soften but not brown or crisp. As the tortillas are softened, transfer them to a plate, stacking them on top of each other.

Once all the tortillas have been softened, cover the plate with plastic wrap or aluminum foil and let cool for about 10 minutes.

To make the enchiladas, preheat the oven to 425°F (220°C) and spray a 9-by-11-inch baking dish with cooking spray.

Place about 3 tablespoons of the filling in the center of a softened tortilla. Roll the tortilla around the filling and place it seam-side down in the prepared baking dish. Repeat until all the tortillas are filled, arranging them in the baking dish with about 1⁄8 inch in between.

Pour 1⁄4 cup of the chili sauce over each enchilada. Bake for 7 to 10 minutes, until the sauce is bubbling.

Garnish each enchilada with about 1 tablespoon of the diced tomato and serve immediately.