In a bowl, whisk together the balsamic vinegar, olive oil, minced garlic, salt, and pepper. Pour this mixture over the skirt steak in a shallow dish. Let it marinate in the fridge for at least 15 minutes.

While the steak marinates, mix together the chopped roasted red peppers, red onion, fresh basil, balsamic vinegar, and a pinch of salt in a small bowl. Stir and set aside.

In another bowl, combine the spiralized or thinly sliced zucchini and cherry tomatoes. Drizzle with olive oil and lemon juice, then sprinkle with salt and pepper. Toss gently.

Heat a grill or grill pan over medium-high heat. Once hot, place the marinated skirt steak on the grill, cooking for about 3-4 minutes per side for medium-rare.

Once the steak is done, let it rest for a few moments before slicing against the grain. Serve topped with red pepper relish alongside the zucchini salad.