Line a large skillet with foil.

Place tomatoes and serrano chiles in the skillet.

Cook over medium-high heat, turning occasionally, until the skins blister and blacken (about 20 minutes for tomatoes, 10 minutes for chiles).

Remove from heat and let cool slightly.

Peel the tomatoes and transfer them to a food processor.

Add the roasted chiles, chopped white onion, and chopped garlic to the food processor.

Blend until a coarse puree forms.

Transfer the sauce to a bowl.

Stir in chopped fresh cilantro, chopped fresh parsley, and fine sea salt.

Prepare a barbecue grill for medium-high heat or preheat your broiler.

Rinse the whole red snapper inside and out with cold water and pat it dry.

Open the fish flat, like a book (butterflied).

Rub the fish inside and out with canola oil.

Sprinkle the inside of the fish with dried Mexican oregano, salt, and pepper.

If grilling, place the fish, opened flat, in a grill basket.

If broiling, place the fish, opened flat, on an oiled rimmed baking sheet.

Grill or broil the fish until it is just opaque in the center, about 6 minutes per side.

Using a spatula, carefully transfer the grilled or broiled fish to a platter.

Sprinkle the fish with fresh lime juice.

Serve the grilled fish immediately with the prepared roasted tomato sauce and warm corn tortillas.