Preheat oven to 350°F (175°C). Grease and line loaf pan with parchment.
In a large bowl, whisk melted butter, brown sugar, and granulated sugar until glossy.
Add eggs, vanilla, and mashed bananas. Mix until smooth.
Fold in flour, baking soda, salt, and cinnamon just until combined.
In a small bowl, mix ube halaya, cream, sugar (if needed), and ube extract until smooth and spreadable.
Pour ⅔ of banana batter into the pan.
Spoon ube mixture in ribbons over the batter.
Add remaining banana batter on top.
Swirl gently with a toothpick—do not overmix.
Bake 55–65 minutes, until a toothpick comes out mostly clean.
Cool 15 minutes in pan, then transfer to a rack.