Preheat the oven to 170 degrees Celsius. Grease the pan with butter on all edges and dust with flour to avoid sticking.
Cream the softened butter and sugar together for 7-8 minutes until the mixture is very light and fluffy, scraping the bowl several times as you mix.
Whisk the eggs, egg yolks, and vanilla in a separate bowl, then add them gradually to the butter mixture while mixing on high speed until the batter is smooth with no liquid streaks.
Add the flour and salt in 2–3 additions, mixing on low speed for about 30 seconds each time, just until the flour is incorporated. If you see any streaks, fold them in gently with a spatula. Do not overmix at this step, or the cake will come out tough.
Pour the batter into the pan, smooth the top with an offset spatula, and tap the pan on the counter to remove air gaps. Bake 60-75 minutes until golden and a toothpick comes out clean, then let the cake cool completely before slicing.