Fill the cocktail shaker with ice.
Add 2 ounces of amaretto, 1 ounce of lemon juice, and 1/2 ounce of simple syrup to the shaker.
If desired, add 1 egg white to the shaker for a frothier texture.
Close the shaker and shake vigorously for 15 seconds.
Place a strainer over the rocks glass and strain the cocktail into the glass.
If using an egg white, gently tap the strainer on the edge of the glass to release any remaining foam.
Garnish with a cherry on top.
Enjoy your Amaretto Sour!