Step 1Mix oil, butter, granulated sugar, brown sugar and eggs in bowl. Stir in buttermilk, then all-purpose flour, whole-wheat flour, salt, baking soda and baking powder. Gently fold in caraway seeds and raisins or berries. Dust in a bit of flour. Or simply dust top with flour.
Step 2Spoon dough into 9-inch cast iron pot or 9-inch springform pan lined with parchment paper. Make a cross by using fingertips to indent. Place on 2 baking sheets stacked together. Bake at 375 degrees until cake is set and springs back when touched with fingertips, 40 to 45 minutes. Remove from oven. Cool in pan.