Cranberry-Ginger Sauce

2 large ruby-red grapefruits
2 tablespoon(s) unsalted butter
1 medium red onion, chopped
1/2 teaspoon(s) kosher salt, plus more to taste
1/2 cup(s) sugar
12 ounce(s) fresh cranberries
1 tablespoon(s) grated fresh ginger

DIRECTIONS

1.Peel about 10 curls of skin from 1 grapefruit, then juice both grapefruits into a bowl; reserve.
2.Melt butter in a pot over medium-high heat and add onion, grapefruit peels, and salt. Sauté until onion is translucent, about 3 minutes. Add sugar, grapefruit juice, and cranberries and bring to a simmer.
3.Continue to simmer until the berries have completely softened, about 12 minutes. Stir in ginger and let cool. Serve at room temperature.