Start the rice first — brown rice takes around 45 minutes.
Marinate the salmon: Whisk paprika, chili powder, cumin, coriander, brown sugar, salt, pepper, olive oil, orange juice, and soy sauce in a glass dish. Add salmon and turn to coat. Scatter chopped cilantro and fresh thyme leaves on top. Fridge 30 min (up to 2 hours).
Preheat oven to 425°F.
Roast the veg: Toss peppers and onion with olive oil, salt, and pepper on a parchment-lined sheet pan. Single layer. Roast 10-12 min until softened with some color.
Make the pico: While veg roasts, dice tomatoes, onion, garlic. Combine with cilantro, salt, and pepper. Set aside to let flavors meld.
Add the salmon: Push veg to one side (or use a second sheet pan if crowded). Place salmon on the pan, spooning some marinade over top. Roast 10-12 min until salmon flakes and internal temp hits 125-130°F for medium.
Sauté the spinach: Heat olive oil in a skillet over medium. Wilt spinach in batches. Season with salt.
Slice the avocado.
Build the bowls: Brown rice bottom → fajita peppers and onions → salmon on top → pile of sautéed spinach → fan of avocado → generous spoonful of pico. Eat immediately.