Preheat your oven to 200°C (390°F). Prepare a large oven-safe dish and spread a layer of sturdy corn chips evenly across the bottom, creating a flat base.
Combine the shredded cheddar and Monterey Jack cheeses in a mixing bowl, then sprinkle generously over the chips, covering them evenly for a gooey cheese layer.
Scatter sliced jalapeños and diced tomatoes evenly on top of the cheese layer, then sprinkle with cumin and chili powder for added flavor.
Drizzle a teaspoon of olive oil over the toppings to help them crisp and enhance the flavor as it bakes.
Place the dish in the oven and bake for 10-12 minutes, or until the cheese is bubbling and golden around the edges, and toppings have roasted slightly.
Remove the dish from the oven carefully with oven mitts, and let it rest for 2 minutes to allow the cheese to set slightly.
Sprinkle freshly chopped cilantro over the hot nachos for a bright, herbal finish, and serve immediately with dollops of sour cream if desired.