How to Make It
Prepare the Summer Relish: Heat 1 tablespoon of the oil in a cast-iron skillet over medium-high. Add corn, and cook, stirring occasionally, until lightly browned, 5 to 7 minutes. Remove from heat, and cool 10 minutes.
Cut corn kernels from cobs; discard cobs. Toss together corn kernels, tomatoes, onion, cilantro, avocado, and jalapeño in a medium bowl.
Whisk together vinegar, lime zest, lime juice, garlic, salt, pepper, and remaining 2 tablespoons oil. Drizzle over corn mixture, and toss to coat. Set aside.
Prepare the Beef Milanesa: Place beef slices on a sheet of plastic wrap on a work surface. Cover with a second piece of plastic wrap, and, using a meat mallet, pound to 1/2-inch thickness.
Combine flour, chopped cilantro, salt, and pepper in a shallow dish. Place beaten eggs in a second shallow dish. Combine panko and cornmeal in a third shallow dish. Dredge beef in flour mixture; dip in egg, shaking off any excess. Dredge in panko mixture.
Heat oil in a large, nonstick skillet over medium-high. Add coated beef slices in a single layer. Cook until deep golden brown, about 3 minutes per side. Serve Beef Milanesa with Summer Relish, lime wedges, and cilantro leaves.