Step 1 Bring the raisins and the Vin Santo to a simmer in a small saucepan, then immediately remove from the heat. Let stand at least 30 minutes, up to overnight.
Step 2 Heat the oven to 400 degrees. Prepare 2 (10-inch) angel food cake pans by generously spraying with cooking spray and dusting with flour.
Step 3Halve the whole oranges through the stem and slice into one-fourth-inch thick sections. Remove any seeds and coarsely chop.
Step 4In the bowl of an electric mixer fitted with the whisk attachment, mix the eggs, the 1 1/4 cups sugar and the leavening over medium high speed until thickened, 3 to 4 minutes.
Step 5With mixer on medium speed, slowly add olive oil in a slow, steady stream down the side of the bowl until emulsified. Turn the mixer back down to low and add the flour and soaked raisins (with any remaining liquid) alternately in 3 batches, scraping down the sides of the bowl as needed. The batter should be thick.
Step 6Remove the bowl from the mixer. Using a rubber spatula, fold chopped oranges into mixture. Set the batter aside for 10 minutes, then distribute evenly between the prepared pans.
Step 7Sprinkle the pine nuts and the remaining one-half cup sugar over the cakes, then garnish with rosemary.
Step 8Bake the cakes for 10 minutes, then lower the oven temperature to 325 degrees and continue to bake, rotating the cakes every 10 to 15 minutes, until golden brown and a toothpick inserted comes out clean, an additional 30 to 35 minutes.
Step 9Run a knife around the inside of the pan and carefully invert it over a large plate to release the cake. Carefully turn it over and transfer it to a large serving plate or cake stand.