Preheat oven to 350 degrees F (175 degrees C). Use Unsalted Butter (1 1/2 tablespoon) to grease the sides and bottom of a 9x13-inch baking pan.
Zest the Sunkist Orange (4) until you have 1 1/2 tablespoons of orange zest. Then peel and slice all the oranges into 1/4-inch thick slices. Place the slices onto the bottom of the greased 9x13 pan in a single layer. You want as little open space as possible. Set aside.
Add orange zest and Granulated Sugar (1 1/2 cup) to a bowl and use your fingers to rub the zest into the sugar until the sugar turns orange and is super fragrant. Set aside.
Add Milk (6 tablespoon) to a small saucepan over medium heat. Add Ground Turmeric (3 teaspoon) and stir well. Heat for 30-40 seconds until the milk is warm. Remove from heat and set aside.
In a medium bowl, whisk together All-Purpose Flour (1 1/4 cup), Baking Powder (1 1/2 teaspoon), Ground Cardamom (1 1/2 teaspoon), and Salt (3/4 teaspoon).
In a separate large mixing bowl, add Egg (6), Orange Zest Sugar, Vanilla Extract (1 teaspoon) and Yuzu Extract (1 teaspoon). Whisk until well incorporated. Add turmeric milk and whisk well. Sift in the dry ingredients and whisk until the flour is just mixed in. Pour in the melted Unsalted Butter (1 1/2 cup) and fold until you have a smooth batter. It's a lot of butter, but trust me, it'll all mix into a smooth batter as you fold!
Pour the batter over the sliced oranges. Tap the baking pan a few times on the table to get rid of any air bubbles. Bake for 30-40 minutes, or until golden brown and a toothpick inserted in the middle comes out clean.
Let the cake cool in the pan for 15 minutes before turning out onto a rack. Cool completely and enjoy!