In a small bowl, mix together the Dijon mustard, ground turmeric, garlic powder, onion powder, black pepper, and salt. Rub the mustard mixture all over the skirt steak, ensuring it's evenly coated. Let it marinate for at least 30 minutes at room temperature or for up to 2 hours in the refrigerator.

In a medium bowl, combine the softened butter, chopped roasted red peppers, parsley, lemon juice, and a pinch of salt and pepper. Mix until well combined. Transfer the butter mixture onto a piece of plastic wrap, shape it into a log, and refrigerate until firm.

Preheat a grill or skillet over medium-high heat. Add the olive oil to the skillet if using. Once hot, add the skirt steak to the grill or skillet. Cook for about 3-4 minutes on each side for medium-rare, adjusting the time based on your desired doneness.

Remove the steak from the heat and let it rest for 5 minutes before slicing. Slice the skirt steak against the grain into thin strips and serve with a generous dollop of roasted red pepper butter on top.