Ube Cake (Filipino Purple Yam Cake w/ Macapuno)

Ingredients

• 4 egg yolks
• 8 fluid ounces ube puree, or ube halaya
• 4 fluid ounces coconut cream
• 1 teaspoon ube extract
• 7 15/16 tablespoons white granulated sugar
• 1/3 teaspoon salt
• 4 fluid ounces carbonated water
• 1 7/8 cups cake flour
• 2/3 tablespoon baking powder
• 1 1/3 teaspoons cream of tartar
• 10 egg whites
• 7 15/16 tablespoons white granulated sugar
• boiling water unchecked▢
• 2 1/2 cups unsalted butter softened and room temperature
• 4 9/16 cups powdered sugar sifted
• 2 fluid ounces coconut cream
• ube extract unchecked▢, optional
• 3 fluid ounces coconut macapuno, string jam