• Preheat oven to 170℃/325°F.

Making the Flan and Caramel

• In a small pot, combine white sugar and water for caramel. Heat over medium until it liquefies and turns amber.
• Pour hot caramel into the baking pan, coating the bottom and sides evenly. Let it cool to set.
• Whisk eggs in a large bowl. Add condensed milk, evaporated milk, vanilla, and salt. Strain into another bowl and set aside.

Making the Process

• Separate egg yolks from whites. In the yolks' bowl, add ube halaya, butter, and ube extract. Stir to combine.
• Sift cake mix into the wet mixture. Stir until just combined. Add food color if desired.
• In a separate bowl, add lemon juice to egg whites. Beat until firm peaks form.
• Gently fold a portion of egg whites into the cake batter, then fold in the rest.

Assembly Process

• Place the pan with caramel into a larger roasting pan.
• Pour flan mixture, then cake mixture over it. Smooth the surface.
• Pour hot water into the roasting pan, about halfway up the side of the round pan.

Baking and Serving Process

• Bake until a toothpick comes out clean, about 45 minutes for a 7-inch pan or 60-65 minutes for a 9-inch pan.
• Let it cool completely, then refrigerate overnight.
• Loosen sides with a spatula and invert onto a serving plate.