3 cups blood orange juice, strained
1 cup granulated sugar
1 cup packed light brown sugar
1 stick unsalted butter, at room temperature
1/3 cup heavy cream
1 teaspoon vanilla extract
1 cup toasted almonds
2 teaspoons sea salt flakes
Line the bottom of an 8-inch square baking dish with parchment paper. Butter parchment paper and set aside.
Place blood orange juice in a 4-quart heavy saucepan and bring to a boil over high heat. Let boil until liquid is reduced to 1/3 cup.
Remove from heat and stir in sugars, butter, and cream. Return to high heat and bring to a boil, stirring constantly. Turn heat to medium and let boil until a candy or deep fat thermometer reads 248 degrees F (or when a half teaspoon placed in a glass of icy cold water turns into a firm, chewy ball), about 17 minutes.
Remove from heat and stir in vanilla.
Scatter almonds on bottom of parchment paper. Pour caramel over almonds. Let sit until cool and firm, about 2 hours. Remove from baking dish and sprinkle salt flakes over top. Cut into 1-inch pieces.