Center a rack in the oven and preheat the oven to 325 (F). Prepare your cake pan by generously spraying with cooking spray.
In a medium bowl, whisk together 1 cup all-purpose flour, 1/2 teaspoon baking powder, and a pinch of salt. Set aside.
In the bowl of a freestanding electric mixer with a paddle attachment, cream together 3/4 cup unsalted butter, 1/3 cup granulated sugar, and 1 teaspoon toasted sesame oil on medium-high speed, until light and fluffy. Once the butter and sugar is light and fluffy, turn the mixer to its lowest speed and slowly add 5 large egg yolks, one at a time, only adding the next egg yolk when the previous one before it has fully incorporated into the batter.
Once the egg yolks have been incorporated, turn off the mixer and whisk together 2 teaspoons vanilla extract and 3/4 cup sweetened condensed milk in a liquid measuring cup. Turn on the mixer to its slowest speed and add the dry ingredients (from the 2nd step) in 3 parts, alternating with the sweetened condensed milk mixture (from the 5th step) in two parts. DO NOT OVERBEAT — simply beat together until all the ingredients have just been incorporated.
Transfer to your prepared cake pan, using a rubber spatula to spread the batter evenly across the pan. Bake in the preheated oven for about 1 hour, or until the top is a dark, golden brown and a skewer inserted into the middle of the cake comes out clean. Cool completely on a wire rack before unmolding.