Position a rack in the middle of the oven and heat the oven to 325°F (180°C). Lightly grease the bottom and sides of a 9-in (23-cm) light-colored metal cake tin with olive oil and line the bottom with a parchment round. Brush the parchment round with olive oil.
The bottom of this cake will become the top of the finished cake. Depending on how you want the finished cake to look, sprinkle sliced almonds around the outside edges of the pan, leaving an empty circle in the center, or spread them out entirely across the bottom of the pan to cover the entire top of the cake. Spread the orange zest evenly over the almonds and the center of the pan.
In a food processor, process the almonds and date sugar until the nuts are a fine powder. Add the baking powder, and pulse to mix it in. Add the honey, vanilla, and almond extract, then process until smooth. Depending on your food processor, this step may require that you stop and scrape the sides down quite a few times before the mixture becomes a smooth paste.
Add the butter, prune puree, and salt. Again, process until smooth, scraping down the walls of the processor as often as needed.
With the food processor running, add the eggs one at a time, and stop the machine once the liquid looks creamy and homogeneous. Finally, add the brown rice flour and pulse just until it’s mixed in.
Scrape the batter into the prepared pan, then gently tap the pan on the counter a few times to eliminate any bubbles.
Bake the cake just until a sharp paring knife comes out clean, for about 45-50 minutes. Place the cake on a cooling rack and run a sharp paring knife around the perimeter to loosen it from the pan. After 15-30 minutes, invert the cake onto a plate or cutting board and then slide it back onto the cooling rack to finish cooling.
Serve on its own, slightly warm or at room temperature. Or top it with a drizzle of honey, unsweetened whipped cream, fresh in-season berries, and bee pollen right before serving.