Step 1: Pat the pork tenderloin pieces dry with paper towels. Season generously with salt and black pepper.
Step 2: Heat 1 tablespoon of olive oil in a large oven-safe skillet (cast iron works great) over medium-high heat. Add the pork nuggets in a single layer, working in batches if necessary to avoid overcrowding. Sear for 2-3 minutes per side until golden brown. Remove the pork from the skillet and set aside.
Step 3: Reduce heat to medium. Add the remaining 1 tablespoon of olive oil to the skillet. Add the chopped red onion and bell peppers. Sauté for 5-7 minutes, stirring occasionally, until they begin to soften. Add the minced garlic and sauté for another 1 minute until fragrant.
Step 4: Pour in the balsamic vinegar and brown sugar (if using). Bring to a simmer, scraping up any browned bits from the bottom of the pan. Let it simmer for 3-5 minutes, or until the balsamic vinegar has reduced slightly and thickened into a glaze.
Step 5: Return the seared pork nuggets to the skillet. Add the fresh rosemary and thyme. Toss everything gently to coat the pork and vegetables evenly with the balsamic glaze.
Step 6: If your skillet is oven-safe, transfer it to a preheated oven at 375°F (190°C) and roast for 10-12 minutes, or until the pork is cooked through (internal temperature reaches 145°F/63°C). If not oven-safe, continue cooking on the stovetop over medium-low heat for 5-7 minutes, stirring occasionally, until pork is cooked.
Step 7: Remove from heat. Taste and adjust seasoning if needed. Garnish with fresh chopped parsley before serving. Serve hot with your favorite side.