Place all marinade ingredients in a small food processor and pulse until pureed.
Place flank steak in a large Tupperware and spread marinade on both sides.
Refrigerate for at least 30 minutes, or ideally overnight.
Once marinated, heat the grill to medium-high.
Brush sweet corn, jalapeño and red onion with olive oil and season with salt and pepper.
Place vegetables on the grill and cook for about 10 minutes, turning every few minutes. For the onion, place flat side down to begin with and then flip once to the curved side. Remove from the grill and let cool for about 10 minutes.
Place steak on the grill and cook approximately 4-5 minutes on each side.
Once cooked, let steak rest for 5 minutes, allowing the juices to settle into the meat.
Once the vegetables are cool, cut the kernels off the cobs, dice the jalapeño (removing the stem and seeds) and dice the onion.
Combine vegetables in a medium bowl with diced tomato, chopped cilantro and lime juice. Season with salt and pepper.
Slice the steak against the grain into thin slices.
Assemble the tacos by filling with a few slices of the steak and top with corn salsa. Serve and enjoy!
For the timing of cooking the vegetables and steak, I prefer to grill the vegetables first and let them cool. While they are cooling, grill the steak. While the steak is resting, chop the vegetables for the salsa. Then you can slice the steak and serve! I also like to throw my tortillas on the grill for a minute on each side to warm them up and give them a little char.