Preheat the Oven: Set your oven to 375°F to ensure it’s ready for baking.
Cook the Sauce: Warm olive oil in a large skillet over medium heat until it starts to shimmer. Add the diced onion and minced garlic, cooking them until aromatic, about 3 minutes. Stir in the oregano, basil, and ancho chile powder to combine the flavors. Mix in the canned tomatoes and a couple of tablespoons of the pickled jalapeño liquid. Let the mixture simmer for around 6 minutes until it thickens slightly. Season with salt and pepper as needed.
Prepare the Filling: In a large bowl, combine the seitan strips, pickled jalapeños, raisins, and 2 cups of the prepared sauce. Mix until evenly coated.
Assemble the Enchiladas: Spread ¼ cup of the remaining sauce across the bottom of a 9 × 13-inch baking dish. In a separate skillet, lightly warm a tortilla for about 10 seconds to make it pliable. Place the tortilla on a flat surface and spread 1 tablespoon of sour cream down the center. Add about ¼ cup of the seitan mixture, sprinkle with shredded cheese, and roll the tortilla tightly. Place it seam-side down into the baking dish. Repeat this process with the remaining tortillas.
Add Sauce and Bake: Once all the tortillas are arranged in the dish, pour the rest of the sauce over the top, ensuring the enchiladas are well-covered. Sprinkle additional shredded cheese across the surface. Cover the dish with aluminum foil and bake for 15–20 minutes.
Garnish and Serve: Remove the foil from the baking dish and let it bake uncovered for a few more minutes to melt the cheese completely. When done, garnish the enchiladas with sliced scallions and fresh cilantro. Serve with extra sour cream on the side for added creaminess.