01 - Boil tomatoes in a pot of water for 5-6 minutes until skins split. Drain and transfer to a blender with garlic, onion, serrano chilies, cumin, salt, and pepper. Blend until smooth. Heat 2 tablespoons oil in a skillet, pour in the tomato sauce, and simmer over medium heat for 7-10 minutes, stirring occasionally until slightly thickened. Adjust seasoning if needed.
02 - Heat a small amount of oil in a separate skillet over medium heat. Lightly fry tortillas one at a time for about 10 seconds per side just until soft and pliable. Drain briefly on paper towels.
03 - Dip each tortilla in the hot tomato sauce, coating both sides completely. Lay on a plate, fill with cheese, and fold in half or roll up. Repeat with all tortillas.
04 - Place 3 entomatadas on each plate. Drizzle with additional tomato sauce, sprinkle with extra cheese, diced onion, and cilantro. Top with a dollop of sour cream or Mexican crema.