Heat 1 tablespoon olive oil in a 12-inch oven proof skillet over medium high heat. Add onions and cook for 3 minutes. Add corn, bell peppers and garlic and sauté for 1 additional minute.: As the oil warms you should see it shimmer, and a faint aroma will rise, signaling readiness; this sheen prevents sticking and encourages gentle caramelization when you add the onion . If the oil smokes heavily the pan is too hot, pull it off the heat for a moment to cool and lower the temp next time to avoid imparting bitterness.
Stir in salsa verde, cream cheese, sour cream, mayonnaise, cumin, paprika, salt and pepper to taste, 3/4 cup Monterey Jack cheese and 1 1/4 cup cheddar cheese. Spread in an even layer and top with remaining cheeses.: You will notice the onion soften and turn translucent while releasing a sweet, savory aroma; stirring occasionally ensures even browning. The sound is a soft sizzle rather than an aggressive pop, which indicates correct heat. Avoid crowding the pan or skipping the stirring or the edges can brown unevenly and develop bitter spots.
Bake at 350 degrees Fahrenheit for 20-25 minutes or until bubbly. Broil for 1-2 minutes until cheese is golden.: The kernels should begin to take on tiny charred flecks and the red bell pepper will soften just slightly, releasing bright, vegetal notes; the garlic will perfume the pan. You want a quick sauté to keep crispness, so be attentive because garlic becomes bitter if left too long, and overcooking will make the peppers too limp.
You can transfer dip to slow cooker to keep warm for 2 hours or serve immediately. Garnish with fresh cilantro and chopped tomatoes if desired.: Once combined the mixture will look glossy and thick, and you should see the cream cheese melt into velvety ribbons while the spices bloom, releasing aromatic warmth. Use a wooden spoon to coax any remaining cheese pockets into the mix; failing to fully incorporate can leave cold pockets of cream cheese that alter texture.
Serve with tortilla chips.: Spreading creates a uniform surface so the top melts and browns consistently; the reserved shredded Monterey Jack and cheddar will form a golden, slightly blistered crust. Watch for high peaks of cheese which can burn; smoothing the surface helps achieve an even color and melt.
Bake at 350 degrees Fahrenheit for 20 to 25 minutes or until bubbly: In the oven you will hear a low bubble, and steam will gently rise when the dip is hot through; that bubbling signals the internal temperature is high enough for a cohesive texture. If it remains cold in the center after the listed time, tent loosely with foil and return for a few more minutes; opening the oven frequently prolongs cooking time.
Broil for 1 to 2 minutes until cheese is golden: Under the broiler the top will transform quickly, taking on a toasty, golden char and crackle that adds visual appeal and a smoky note. Stand nearby and watch constantly because broiling can go from perfect to burned in seconds; if you are nervous, move the rack down one level and extend the time slightly.
You can transfer dip to slow cooker to keep warm for 2 hours or serve immediately: Transferring to a warm slow cooker maintains a gentle heat that prevents drying while keeping the dip scoopable; you will notice a slow, steady shimmer rather than vigorous bubbling. Avoid leaving it on high without stirring, which can cause separation or scorching along the edges.
Garnish with fresh cilantro and chopped tomatoes if desired: The bright green cilantro and juicy diced tomatoes add a fresh contrast to the rich, cheesy base and restore lift to each spoonful. Add them just before serving so they retain color and texture; pre adding will make them limp and diminish their vibrancy.
Serve with tortilla chips: Use sturdy tortilla chips and scoop from the center to get a balanced bite of melted cheese and corn; the crunch versus the silky dip is part of the joy. Thin chips may shatter, so choose thicker chips or small pieces for dipping to avoid messy spills.