Position rack in center of oven and preheat the oven to 400°F.
Lightly grease a large baking dish with 1 tablespoon of the oil. Set aside.
In a blender, puree the tomatoes on high speed.
In a medium skillet, heat 2 tablespoons of the remaining oil over medium-high heat. Add the onion, cumin, oregano, and Baby Bam and cook, stirring, until soft, about 4 minutes.
Add the garlic and cook, stirring, for 1 minute.
Add the pureed tomatoes. Reduce the heat to medium-low and cook, stirring, until slightly thickened, about 5 minutes.
Season with the salt and pepper and stir.
Reduce the heat to very low. Simmer to keep warm, stirring occasionally, while you assemble the enchiladas.
Heat a second medium skillet over low heat.
Place the remaining 2 tablespoons of the oil in a small bowl or dish.
With a pastry brush, lightly brush both sides of each tortilla with the oil.
Place one tortilla at a time in the skillet until just warm and softened, about 2 to 5 seconds per side.
Remove tortilla with tongs and place it on a large plate. Continue with the remaining tortillas and oil.
Combine the white and yellow Cheddar cheeses in a medium bowl.
Sprinkle 1/4 cup of the mixed cheese in a line along the middle of each tortilla.
If using the finely chopped raw onion, sprinkle a heaping teaspoon into each tortilla.
Fold one side toward the middle to enclose the filling, then roll up the tortilla to form a cylinder.
Place tortillas seam side down in a single layer in the prepared baking dish.
Pour the tomato sauce over the filled enchiladas, spreading with the back of a spoon to distribute evenly.
Sprinkle the remaining 1 cup of cheese over the top of the enchiladas.
Bake until bubbly, about 10 to 12 minutes.
Using oven mitts or pot holders, remove the baking dish from the oven and let sit for 5 minutes before serving.
To serve, divide enchiladas among plates and garnish, if desired, with the cilantro.
YIELD: 12 enchiladas, serving 6 to 12