Make-ahead: This salsa can be made up to 24 hours in advance and stored in an airtight container in the refrigerator. Stir before serving and let sit at room temperature for 10 minutes before plating. Heat level: For mild salsa, remove all jalapeño seeds and membrane. For extra heat, substitute a serrano pepper or leave jalapeño seeds in. Fruit tips: If fresh peaches are out of season, thawed frozen peaches patted dry work well. Ataulfo (champagne) mangoes offer the sweetest, creamiest result. Mellow the onion: Soak diced red onion in cold water for 5 minutes, then drain, if you prefer a milder onion flavor. Storage: Keeps in an airtight container in the refrigerator for up to 3 days. Does not freeze well.