This scrumptious cake has a rustic elegance that lets you imagine yourself in a charming farmhouse in the Tuscan wine country. Yellow cornmeal (aka polenta) gives it a delightfully distinctive grainy texture; pure olive oil makes it rich and ultra-moist; and the fresh red grapes it is studded with not only look like edible gems, the fruit tastes even sweeter and plumper once baked. Sit down and savor this cake with an espresso, a cup of tea, or even a glass of fruity wine.
Preheat the oven to 325°F. Brush a 10-inch cast-iron or other ovenproof skillet with olive oil. Whisk together the flour, cornmeal, baking powder, and salt in a medium-size bowl.
Beat the olive oil, honey, and eggs in another medium-size bowl until incorporated. Stir in the vanilla and lemon zest, then add the flour mixture in three batches, stirring to incorporate after adding each batch. Stir in half of the grapes. Transfer the batter to the skillet and bake, in the middle of the oven, for 10 minutes, then scatter the remaining grapes on top of the cake and continue to bake until it is golden and a toothpick inserted into the center comes out clean, 20 to 25 minutes more.
Remove from the oven and let rest in the skillet for 10 to 15 minutes before sprinkling with confectioners’ sugar, if desired, and cutting into eight wedges. The cake will keep for a week in an airtight container in the refrigerator.