Step 1: Rinse each prickly pear under cool running water, cut off both ends, slice the skin lengthwise, peel away the thick outer layer, and chop the fruit into 2-inch chunks.

Step 2: Roll each lemon on the counter, cut in half, and juice using a citrus juicer or reamer to yield about 1/2 cup of fresh lemon juice.

Step 3: Place the chopped prickly pear chunks in a blender and blend on high speed for about 30 seconds until completely smooth.

Step 4: Set a fine mesh strainer over a bowl and pour the blended puree through it, pressing with the back of a spoon to extract all juice and leave seeds and pulp behind.

Step 5: Pour the strained prickly pear juice and fresh lemon juice into a large pitcher and stir to combine.

Step 6: Add 4 cups of cold water and 1/4 cup granulated sugar to the pitcher, stirring for about 30 seconds until the sugar dissolves completely.

Step 7: Stir in 1/8 teaspoon of salt, taste, and adjust seasoning if needed to enhance the fruit flavors.

Step 8: Fill glasses with ice cubes, pour the prickly pear lemonade over the ice, garnish with fresh mint leaves and lemon slices, and serve immediately.