For the clearest caramel and smoothest custard, ceramic or glass baking dishes work best for cooking this Filipino-American–style dessert.
- 8 servings
- 1 small grapefruit
- 1 2/3 cups sugar, divided
- 4 large eggs
- 5 large egg yolks
- 1 1/3 cups heavy cream
- 1 1/3 cups whole milk
- 1/4 teaspoon kosher salt
- Finely grate zest from grapefruit; set aside. Cut away peel and white pith from flesh; discard. Working over a bowl, cut along membranes to release segments into bowl; discard membranes. Set segments aside.
- Cook 1 cup sugar in a small saucepan over medium heat until it begins to melt and turn brown around the edges. Using a heatproof rubber spatula, pull melted sugar at edges toward center of unmelted sugar. Continue cooking, pulling in melted sugar, until all the sugar is melted and caramel is uniformly dark brown (it should smell toasty but not burnt), 10–12 minutes total (if you still have undissolved lumps of sugar, stir off heat until they melt). Divide caramel between two 8″-diameter shallow ceramic ovenproof baking dishes or two 9×5″ loaf pans, preferably glass or ceramic, to create a 1/8″–1/4″ deep layer. Let cool.
- Place a rack in middle of oven; preheat to 275°F. Bring a large pot of water to a boil. Purée eggs and egg yolks with remaining 2/3 cup sugar in a blender until smooth and sugar is dissolved, about 1 minute. Transfer to a large bowl and gently mix in cream, milk, salt, and reserved grapefruit zest; let sit 5 minutes. Strain into a large measuring glass. Divide custard between prepared baking dishes.
- Line a roasting pan with a thick kitchen towel; this will keep baking dishes from sliding and will insulate flan, preventing it from overcooking. Set dishes on towel and place roasting pan in oven. Pour very hot water into pan until it reaches the same level as flan in baking dishes. Bake flan until it looks set like Jell-O (it will wobble when gently shaken), 40–55 minutes. Transfer dishes to a wire rack; let flan cool.
- Run a small knife around edges of flan to loosen. Invert onto a platter and top with reserved grapefruit segments.
- Do Ahead
- Flan can be made 1 day ahead. Cover and chill. Unmold and bring to room temperature before serving.