Heat your oven to 425°F (220°C) or set your toaster oven to “Bake.” If you're using an air fryer, preheat to 375°F (190°C).
Split the English muffins and lightly toast them for 2–3 minutes until just crisp. This prevents soggy bottoms (no one asked for that).
Spread 1–2 tablespoons of pesto on each muffin half. Don't drown it—pesto is potent.
Add chopped spinach, bell pepper, onion, olives, and cherry tomatoes. Keep it even for clean bites.
Top with mozzarella and a sprinkle of Parmesan. A little crushed red pepper if you like drama.
Oven/toaster oven: 8–10 minutes until cheese melts and edges crisp. Air fryer: 5–7 minutes (check early so you don't incinerate lunch).
Squeeze a little lemon over the top, season with salt and pepper, and drizzle a touch of olive oil if you're feeling fancy.
Let them cool for 2 minutes, then demolish responsibly.