Prep the cucumber and onion: Toss the diced cucumber with 1/2 teaspoon of salt and let it sit in a fine-mesh strainer over a bowl for 10 minutes. This draws out extra water so your salad stays creamy. Pat dry. Meanwhile, soak the diced red onion in cold water for 5 minutes to tame sharpness. Drain and pat dry.
Char the corn: Heat a cast iron or non-stick skillet over medium-high heat. Add the corn in a single layer. Let it sit for 2-3 minutes without stirring until dark spots appear. Stir and let another side char. Listen for popping sounds — that’s the sugars concentrating. Transfer to a plate to cool.
Make the dressing: In a large mixing bowl, whisk together mayonnaise, sour cream, lime zest, lime juice, chili powder, cumin, and a pinch of salt and pepper. Smell it — it should be bright and slightly spicy. If it smells flat, add another pinch of salt.
Combine: Add the shredded chicken, cooled corn, drained cucumber, soaked onion, cotija cheese, and cilantro. Fold gently with a spatula until everything is evenly coated. Don’t stir too hard — keep the chicken in nice shreds.
Taste and adjust: Add more salt, lime, or chili powder until it tastes bright and balanced. I almost always add a little more lime juice here.
Chill (optional): Let the salad rest in the fridge for 20-30 minutes for flavors to meld. It can be served immediately, but the texture and flavor improve with a short chill.