Preheat oven to 425°F (220°C). Slice pork tenderloin into 1-inch thick medallions and pat dry with paper towels.
Toss peeled carrots with 1 tablespoon olive oil, salt, pepper, and fresh thyme if using. Spread in a single layer on a parchment-lined baking sheet.
Roast carrots in the oven for 20-25 minutes, stirring halfway through, until tender and slightly caramelized.
While carrots roast, heat remaining 1 tablespoon olive oil in a large skillet over medium-high heat.
Add pork medallions in a single layer without crowding and sear for about 3 minutes per side until golden brown but not fully cooked.
Remove pork from skillet and set aside. Lower heat to medium and add minced garlic; stir for 30 seconds until fragrant.
Whisk in Dijon mustard, honey, and apple cider vinegar. Simmer gently for 2-3 minutes until glaze thickens and becomes glossy.
Return pork medallions to skillet, spoon glaze over them, and cook for another 2-3 minutes, flipping once, until pork reaches 145°F (63°C) or is slightly pink inside.
Plate pork medallions with roasted carrots and spoon extra glaze over the top. Optionally garnish with fresh parsley or a squeeze of lemon juice.
