Season skirt steaks with salt and pepper. Set aside while you make the chimichurri.
Heat ½ tbsp olive oil in cast iron skillet, and grill peaches until charred. Remove from heat, let cool, and dice. Combine peaches and remaining chimichurri ingredients in a bowl. Set aside
For skirt steaks, heat cast iron skillet over medium heat. Add olive oil and butter. When butter begins to foam, add skirt steaks and sear, 6-7 minutes on each side, until caramelized. Thermometer should read 110° degrees for medium rare, or 115° degrees for medium. Remove onto cutting board and allow to rest for 3 minutes.
To serve, slice steaks and top with a generous amount of chimichurri.