Grilled Skirt Steak with Mustard Greens Chimichurri

Ingredient:

• 8 ounces fresh mustard greens (from 1 bunch), trimmed and chopped
• 6 cilantro sprigs, roughly chopped
• 1/4 cup finely chopped shallot
• 1 medium garlic clove, finely chopped
• 2/3 cup extra-virgin olive oil
• 1 medium Fresno chile, finely chopped (about 1 1/2 tablespoons)
• 1 1/2 teaspoons fresh lime zest
• 1/3 cup red wine vinegar
• 1 teaspoon kosher salt
• 1/4 teaspoon black pepper
• 1/4 cup extra-virgin olive oil, plus more for greasing
• 3 garlic cloves, grated
• 1 tablespoon kosher salt, divided
• 1/2 teaspoon black pepper
• 1/2 teaspoon onion powder
• 2 skirt steaks (about 1 1/4 pounds each)
• Flaky sea salt, for garnish