Prep the mangos: Peel and dice into small cubes.
Aim for pieces about the size of corn kernels so every bite is balanced.
Dice the veggies: Finely chop red onion, jalapeño, and bell pepper. Keep the jalapeño seeds out for mild heat; leave some in if you like it spicier.
Chop cilantro: Roughly chop the leaves and tender stems.
Combine the base: In a medium bowl, add mango, onion, jalapeño, bell pepper, and cilantro.
Add lime and seasoning: Squeeze in lime juice, then add cumin, a good pinch of salt, and a few grinds of pepper. Toss gently to coat.
Fold in avocado last: Dice the avocado and gently fold it into the salsa.
Taste and adjust lime, salt, and heat as needed.
Rest briefly: Let the salsa sit for 5–10 minutes to meld flavors. Serve chilled or at room temperature.