1. In a food processor, blend parsley, oregano, garlic, olive oil, apple cider vinegar, lemon juice, smoked paprika, red pepper flakes, salt, and black pepper until smooth. Set chimichurri aside.
2. Pat flank steak dry. Season generously with salt and pepper.
3. Heat a skillet over medium-high heat, add oil, and sear steak 4 minutes per side for medium-rare. Let rest 10 minutes, then slice against the grain.
4. Toss cherry tomatoes and red onion in a pan until caramelized (5 minutes). Blanch baby spinach in boiling water 30 seconds, then drain.
5. Plate steak with chimichurri, roasted veggies, and spinach. Serve immediately.