While the grill heats to medium-high, prepare all your ingredients so assembly is seamless. Mince the garlic cloves finely, zest and juice the limes, slice the scallions into thin 1/8-inch rounds, seed and finely dice the jalapeño into 1/4-inch pieces, crumble the cotija cheese into small pea-sized pieces, and roughly chop the cilantro. I like to keep the jalapeño separate from other ingredients so you can control the heat level when tossing—some people prefer less spice!
Lightly brush the corn ears with olive oil on all sides to prevent sticking. Place them on the medium-high grill and cook for 2 minutes per side, rotating a quarter turn each time, until you get nice charred marks and the kernels begin to soften. The char creates sweet, caramelized flavors that are essential to street corn's appeal. Once charred, set the corn aside to cool enough to handle, about 2-3 minutes.
In a medium bowl, whisk together the mayo, minced garlic, lime zest, and lime juice until smooth and well combined. This crema base will coat the corn kernels and provide the rich, tangy foundation for the entire salad. The garlic will distribute evenly through the mayo, ensuring every bite has balanced flavor.
Once the corn is cool enough to handle, stand each ear upright on a cutting board and use a sharp knife to cut the kernels off in long, downward strokes, rotating as you go. Add the kernels to the bowl with the prepared scallions. Pour the lime crema from Step 3 over the corn and scallions, and toss gently to coat everything evenly. I find that tossing when the corn is still slightly warm helps the dressing coat the kernels better.
Gently fold in the crumbled cotija cheese, cilantro, smoked paprika, diced jalapeño, salt, and cayenne pepper. Toss everything together until the seasonings are evenly distributed. The cheese should remain in small pieces rather than melting, so avoid overmixing. Taste and adjust the salt or cayenne if needed—remember that cotija adds saltiness, so go easy at first.
Transfer the Mexican street corn salad to a serving bowl or individual plates. Serve immediately while the corn is still warm and the flavors are bright and vibrant. This salad is best enjoyed fresh, though any leftovers can be refrigerated for up to 2 days.