Wash 6 fresh limes. Zest two or more limes until you have one tablespoon of lime zest. Set that aside.
Cut 4-6 limes in half and squeeze the juice into a measuring cup. You'll need ½-3/4 cup depending on your preference.
Fill your blender with 2 cups of cold water, 6 cups of ice, ½ cup of lime juice, 1 tablespoon of lime zest, and one 14 ounce can of sweetened condensed milk.
Blend the mixture on high for 60-90n seconds. The lemonade will be frothy with ice crystals, but mostly smooth.
Serve immediately and garnish with a lime wedge.
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Notes
This recipe is written with ½ cup of fresh lime juice. For more tangy lime flavor, add more lime up to ¾ cup if desired.