Gather the supplies. the quantity in the supplies list makes 1 cocktail.
fill the shaker with ice.
add the gin and simple syrup.
pour in the lemon juice.
shake until the outside of the shaker is frosted.
serve in a cocktail glass. garnish with a slice of lemon.
As a variation, add a few dashes of Angustura Bitters and call it Fitzgerald Cocktail