Combine grapefruit and lemon juices, Simple Syrup, egg whites, bitters, pamplemousse liquer and tequila into a mixing glass.
Cap, then dry shake vigorously 30X.
Remove cap. Add the scoop of Ice.
Cap again, then shake vigorously 20X, until chilled.
Remove cap.
Strain drink into a chilled martini glass.
Garnish with a grapefruit half moon on the rim of the glass, as shown in the photo.