Preheat oven to 350°F (175°C). Grease an 8x8-inch (20x20cm) square pan with oil. I have used a glass baking pan but you can also use aluminum baking pan.
In a bowl, mix together softened butter, sugar, and condensed milk using a whisk until it is smooth and combined. Scrape down the sides of the bowl.
Add room temperature milk and vanilla, mix well until fully combined.
Sift in the dry ingredients (flour, baking powder, baking soda, salt) and mix until just combined. Avoid over mixing. Scrape down the bowl once more to ensure everything is incorporated.
Pour batter into the greased pan and bake for 20–22 minutes, or until a toothpick inserted comes out clean.
While baking, prepare the saffron milk soak.