Using a food processor or blender, add all of the ingredients except for the steak; pulse until smooth.
Place flank steak in a large re-sealable bag. Add marinade, turning several times to coat. Refrigerate for 1 hour. (Note: When about 30 minutes remain on the marinating time, go ahead and start making the corn salsa.)
Remove steak from bag; discard marinade.
Place steak on grill (medium-high temperature). Grill for 4-6 minutes per side, or until steak is done to taste.
Transfer steak to a large cutting board and let rest for 5 minutes; slice steak against the grain into strips.
Top with corn salsa before serving.
For the Charred Corn Salsa
Preheat grill to medium-high heat.
Grill corn, rotating occasionally, for 10-12 minutes, or until lightly charred.
Let corn cool and then slice kernels into a large bowl. Add remaining salsa ingredients (diced onion, jalapeno, cherry tomatoes, cilantro, lime juice, salt and pepper); stir until well combined. Set salsa aside.
Notes
For a spicier marinade, leave the seeds and ribs in the jalapeno. For a milder version, use a paring knife to remove the ribs and seeds before adding the jalapeno to the food processor.