Step 1

For the dressing: Blend the buttermilk, mayonnaise, chives, cilantro, parsley, sugar, garlic, lime juice and avocado in a blender or food processor until smooth, adding salt and pepper to taste. Set aside.

Step 2

For the corn and tomato salad: Heat an oiled grill, grill pan or large skillet over medium-high heat.

Step 3

Oil the tomatoes, corn, lime and onion with the olive oil and sprinkle with salt and pepper. Grill the tomatoes for 8 minutes, until charred and juicy; remove to a bowl. Grill the corn, onion and lime on all sides for a few minutes, until char marks appear. Remove to a cutting board.

Step 4

When cool enough to handle, cut the kernels off the cob and season with salt and pepper. Slice the onion into half-moons. Add the corn and onions to the tomatoes and toss with the oregano, red pepper flakes and the juice from one of the lime halves.

Step 5

Spread the dressing on the bottom of a wide shallow bowl. Top with the veggies and sprinkle with Cotija and cilantro leaves. Garnish with other lime half.