In a large skillet, heat 1 tablespoon of olive oil over medium heat. Once hot, add the diced onion and sauté until translucent, about 3-4 minutes. Add the minced garlic and cook for an additional minute until fragrant.
Gradually add the fresh spinach to the skillet. Cook, stirring occasionally, until the spinach is wilted and reduced in volume, about 3-5 minutes.
Remove the skillet from heat. In a mixing bowl, combine the sautéed spinach mixture with fresh lime juice, chopped cilantro, green chiles, ground cumin, chili powder, sour cream (or Greek yogurt), salt, and black pepper. Mix until well combined, then stir in 1 cup of shredded Monterey Jack cheese and 1 cup of shredded Cheddar cheese.
Preheat your oven to 350°F (175°C). Spread half of the enchilada sauce on the bottom of a 9x13 inch baking dish. Take a flour tortilla and spoon a generous amount of the spinach and cheese mixture along the center. Roll the tortilla tightly and place it seam-side down in the baking dish. Repeat with remaining tortillas and filling.
Once all the tortillas are in the baking dish, pour the remaining enchilada sauce over the top. Sprinkle the remaining Monterey Jack and Cheddar cheeses evenly over the sauce.
Cover the baking dish with aluminum foil and bake in the preheated oven for 20 minutes. Remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and lightly golden.
Once baked, remove the enchiladas from the oven and let them cool for a few minutes. Serve warm, topped with chopped green onions, fresh cilantro, and diced avocado for an extra burst of flavor and color.
