Cook the pasta: Bring a large pot of salted water to a boil. Cook pasta until just al dente. Drain and rinse under cool water to stop the cooking. Toss with a drizzle of oil to prevent sticking and set aside to cool.

Char the corn: Heat a large skillet over medium-high. Add a little oil, then the corn in an even layer. Let it sit to develop color, then stir occasionally until lightly charred in spots, 5–7 minutes. Season with a pinch of salt. Cool slightly.

Make the dressing: In a large bowl, whisk mayonnaise, sour cream, lime zest and juice, chili powder, smoked paprika, cumin, minced garlic, honey, 1/2 teaspoon salt, and a few grinds of pepper. Adjust lime and salt to taste; it should be bright and well-seasoned.

Prep the add-ins: Chop cilantro and scallions. Dice red onion and jalapeño. Crumble Cotija.

Combine: Add cooled pasta and corn to the dressing. Fold in red onion, jalapeño, cilantro, and most of the Cotija, reserving a little for garnish. If using tomatoes or avocado, gently fold them in last.

Taste and tweak: Add more lime, salt, or chili powder as needed. If you like heat, a few dashes of hot sauce work well.

Chill or serve: Cover and chill for 30 minutes for best flavor, or serve right away at room temperature. Garnish with remaining Cotija, extra cilantro, and a sprinkle of Tajín if you like.