In a large skillet, heat the olive oil over medium heat. Add the diced onion and sauté until it becomes translucent, about 3-4 minutes. Add the minced garlic and cook for an additional minute, until fragrant.
Add the fresh spinach leaves to the skillet and cook until wilted, stirring occasionally, about 3-5 minutes. Remove from heat and let cool slightly.
In a mixing bowl, combine the sautéed spinach mixture with lime juice, chopped cilantro, green chiles, cumin, chili powder, sour cream (or Greek yogurt), salt, and black pepper. Mix until well combined. Fold in 1 cup of Monterey Jack cheese and 1 cup of Cheddar cheese.
Preheat your oven to 350°F (175°C). Spread 1 cup of green chile enchilada sauce evenly on the bottom of a 9x13 inch baking dish. Take a tortilla, spoon about 1/3 cup of the spinach and cheese filling down the center, and roll it up tightly. Place the rolled tortilla seam-side down in the baking dish. Repeat this process until all the tortillas and filling are used.
Once all the enchiladas are in the baking dish, pour the remaining green chile enchilada sauce over the top. Sprinkle the remaining Monterey Jack and Cheddar cheese evenly over the sauce.
Cover the baking dish with aluminum foil and bake in the preheated oven for 20 minutes. After 20 minutes, remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and golden.
Once baked, remove from the oven and let cool for a few minutes. Top with chopped green onions, fresh cilantro, and diced avocado before serving. Enjoy!