Preheat the oven to 180 °C / 355 °F (or 160 °C if using a fan). Grease and line the bottom of two 12-inch round cake tins. Leave them ready as if they're waiting for a big date. Only have one cake tin? Don't worry, my notes below are ready to rescue you.
In a small bowl or jug, mix the eggs, vanilla, almond extract, milk, and sour cream together thoroughly. Use a fork to combine everything—it might look strange and a bit lumpy, but don't stress. That’s perfectly normal. Once mixed, set it aside until you need it.
Sieve the flour, cornflour, and baking powder directly into the mixer bowl. Add the sugar and salt, and give them a little stir together. Turn the mixer to medium-low (or medium-low speed, because we're not in a dragon's kitchen) and add the cubed butter, one at a time. Keep beating until all the flour hugs the butter and the mixture looks like breadcrumbs. Don't forget to scrape the sides of the bowl, nobody gets left behind here.
Turn the mixer to low speed and, with the patience of a saint, gradually add half of the sour cream mixture. Turn the speed-up to medium and let everything blend until smooth and undramatic, about a minute or so. Scrape the edges of the bowl (again, because yes, there is always a stubborn ingredient), lower the speed and add the rest of the sour cream mixture. Give it another 30 seconds on low speed, just enough to mix it all together properly.
Divide the batter by eye between the two tins and bake for 50–60 minutes, or until a toothpick comes out clean in the centre, like a triumphant hero. Make sure it's well done before you take it out, because a sunken, moist cake doesn't make anyone happy. Leave them to cool in the tins on a wire rack. Once they are cool enough not to burn your fingers, carefully take them out and let them cool completely. Then fill and top with the icing of your heart's desire.