Steak and salsa:
Prepare a grill for medium-high heat; oil grate. Grill corn, turning occasionally, until lightly browned all over, 8–10 minutes; let cool. Cut kernels from cobs and place in a medium bowl. Add onion, jalapeño, tomatoes, cilantro, and lime juice to corn and toss to combine; season with salt and pepper. Set salsa aside.