In a small mixing bowl, combine the chili powder, smoked paprika, and cayenne pepper. Set aside.
Place a large skillet over medium heat and add the extra virgin olive oil. Once shimmering, add the chopped yellow onion and sauté for about 3 minutes until translucent.
Add the 2 cups of raw corn kernels to the skillet. Cook for 5 minutes, stirring occasionally to allow caramelization. Stir in the chopped garlic, salt, and pepper during the last minute.
Reduce the heat to low. Add the room temperature cream cheese, sour cream, and half of your prepared spice mixture. Stir constantly until the cheese melts and the dip is smooth.
In a small saucepan over medium-low heat, melt the salted butter. Whisk in the remaining half of the spice mixture. Let it bubble gently for 30 seconds to toast the spices, then remove from heat.
In a separate small bowl, whisk together the mayonnaise (or Greek yogurt) and fresh lime juice.
Transfer the warm corn and cheese mixture into a shallow serving dish and smooth the top. Dollop the lime mayo over the top and gently swirl it across the surface.
Drizzle the spicy melted butter all over the top, swirling it into the mayo for a marbled look. Garnish with the grilled corn kernels, crumbled cotija cheese, and fresh cilantro. Serve immediately with sturdy tortilla chips.