Brown the ground beef and diced onion over medium heat until the beef is no longer pink and the onions are translucent. Drain any excess grease or moisture.: As you cook, listen for a steady sizzle and watch for the beef to break into small crumbles with a deepening brown color, these browned bits give savory intensity. The onions should turn soft and slightly translucent, releasing a sweet, savory scent that mixes with the beef aroma. Use a spatula to break the meat into even pieces so it cooks uniformly. The why here is that browning creates Maillard reaction flavors, which are essential for a rich, layered finished dish. A common misstep is turning the heat too low, which causes steaming rather than browning, yielding bland meat. If there's a lot of fat, remove it after cooking to prevent a greasy final texture. If you accidentally dry the pan out, add a splash of the enchilada sauce later to bring moisture back.
Place the skillet back on the stove over medium heat. Add the garlic powder, salt, enchilada sauce, green chiles, and sour cream. Mix well.: Once everything is combined you will notice the sauce start to coat the meat evenly, transforming loose browned crumbles into a cohesive filling. The scent will shift, becoming tomato forward with a warm chile undertone and a gentle tang from the sour cream . Stir until you see a uniform color and texture, this ensures every bite is balanced. The reason for adding these seasonings now is to let them bloom in the residual heat and fat, marrying flavors. A pitfall is adding the sour cream at too high a heat, which can make it separate, so keep the pan at moderate temperature. If separation occurs, lower the heat and stir gently until it smooths back together.
Bring sauce to a boil and then lower heat and simmer for 4-6 minutes or until thickened.: As the sauce comes to a brief boil you will see bubbles rise and the aroma will intensify, indicating moisture is evaporating and flavors are concentrating. Lowering to a simmer lets the sauce reduce without scorching, and you should watch for it to become visibly thicker, clinging to the meat rather than pooling. This step amplifies the sauce flavor and prevents a watery final skillet. A common mistake is leaving the heat too high which can burn sugars in the sauce, producing bitterness. Stir occasionally to keep the bottom from sticking, and if the sauce seems to reduce too quickly, drop the flame and cover loosely for a short period.
Stir in half the cheese to the meat mixture, then sprinkle the other half on top. Place the lid on the pan for 2-3 minutes or until the cheese is melted.: When you fold some of the cheddar cheese into the warm filling it becomes glossy and creamy, adding richness throughout. The remainder on top melts into a golden, gooey layer that signals comfort and indulgence. Covering the pan traps heat and creates a gentle steam that finishes the melting without overcooking the meat. The sensory cue is the cheese becoming uniformly gooey and slightly shiny, with occasional little bubbles at the edge. Avoid leaving the pan unattended on high heat, because the bottom can scorch while the top looks melted. If the cheese needs a touch more melting, reduce heat and cover a bit longer rather than increasing temperature.
Remove from heat and top with black olives and green onions if desired.: The final act introduces fresh and briny contrast, the sliced black olives lending a soft, slightly salty chew, and the diced green onions offering a crisp, bright lift. Once off the heat the skillet will continue to settle and the residual warmth will meld the toppings without wilting them. Visually you want dark olive slices and vivid green rings scattered across the melted cheese, creating a pleasing contrast. One mistake is adding toppings too early, which can soften them excessively and mute their fresh qualities. Let the skillet rest a minute so the flavors marry, then serve straight from the pan for a communal, satisfying experience.