Buzz

In a small stockpot, warm vinegar over medium-high heat. When vinegar reaches 150°F on an instant-read thermometer, and just before it starts to simmer (after about 5 minutes), add lemon slices and continue to cook until lemon peels begin to soften and wilt, about 10 minutes more.

Whisk in black pepper, cayenne, pepper flakes, and sugar. Continue to cook over medium-high heat until sugar is completely dissolved and sauce reaches 190°, about 10 minutes. Remove from heat and allow to cool completely before using. Once the lemon is removed, the sauce can be refrigerated in an airtight container for up to 8 weeks.