1. Dry out the tortillas. Lay the tortillas in a single layer, cover with a dish towel or napkin and let them dry for about a half hour (depending on their moistness) until they are leathery—this will enable them to crisp thoroughly on the grill.
2. Make the spicy avocado mayo. In a food processor, combine the egg yolks and lime juice. Cover and turn on, then with the food processor running slowly drizzle a thin stream of the oil through the feed tube—the yolks and oil should emulsify and become creamy. Add the avocado, green chile and cilantro. Let the processor run for another 20 seconds to ensure the additional ingredients are incorporated. Taste and season with salt, usually about 1 teaspoon.
3. Prepare the bacon and heirloom tomatoes. In a large (10-inch) skillet, cook the bacon over medium heat, stirring occasionally, until well browned, about 10 minutes. Remove the bacon and drain on a paper towel. Strain the fat into a small bowl—you need ¼ cup bacon fat (if you’re lacking, add vegetable oil). Scoop the diced heirloom tomatoes into a serving bowl.
4. Grill and serve the tlayudas. Turn on a gas grill to medium or light a charcoal fire and let the coals burn until medium hot and covered with grey ash. When you’re ready to serve, lay several tortillas on the grill and turn every 20 seconds or so until nearly crisp—this should take a couple of minutes depending on the heat of your fire. Brush the top of each tortilla generously with the bacon fat or oil and let the tortillas crisp a little longer, then remove them to a serving platter. Spread on some spicy avocado mayo and top with the tomatoes. Sprinkle each tostada with about a tablespoon of bacon, garnish with cilantro leaves and immediately serve to your guests while you make the next round.