Preheat the oven to 350°. Butter and flour a 9-inch-square cake pan. In a bowl, whisk the flour with the baking soda and salt. In a bowl, beat the butter with the sugar until smooth. Beat in the yogurt, followed by the eggs, lemon zest, lemon juice and vanilla. Gradually beat in the dry ingredients until blended.
Scrape the batter into the prepared pan and bake for about 45 minutes, or until golden brown and a cake tester inserted in the center of the cake comes out clean. Transfer the cake to a rack to cool for 10 minutes, then invert the cake onto the rack and let cool completely. Dust with confectioners’ sugar before serving.
Sliced pears tossed in a little lemon juice.
A lively Late Harvest Riesling from California will echo this cake’s tangy sweetness.