Breton Butter Cake

Preheat the oven to 350°F. Cream the butter and sugar in the bowl of an electric mixer fitted with paddle attachment until light and fluffy. Beat in the vanilla and yolks 1 at a time, beating well after each addition. Add the flour and salt; beat just until combined. Do not overmix.

Transfer the batter to a 9-inch tart pan with a removable bottom; with a small offset spatula, spread the batter and smooth the top. (If necessary, chill the batter 10 minutes before smoothing.) Place the pan in the refrigerator 15 minutes.

Remove from the refrigerator. Brush the top with beaten egg, and mark a criss-cross pattern with a fork. Brush again with the egg. Bake until the cake is deep golden brown and the edges pull away from the sides of the pan, about 50 minutes.