How to Make It
Preheat the oven to 350°. Brush a 10-inch springform pan with butter. Line the bottom of the pan with parchment paper and butter the paper.
Put the oranges in a microwave-safe bowl; add enough water to reach halfway up the side. Cover partially with plastic wrap. Microwave on high power, turning the oranges every 3 minutes, until very soft, about 15 minutes; drain. Quarter the oranges, discarding any seeds. In a food processor, puree until smooth, 2 to 3 minutes.
In a large bowl, beat the eggs with the granulated sugar. Whisk in 1 1/2 cups of the orange puree. Using a spatula, fold in the coconut, almond flour and baking powder. Scrape the mixture into the prepared pan and smooth the top. Sprinkle the sliced almonds over the cake and bake until a toothpick inserted in the center comes out with a few moist crumbs attached, about 45 minutes. Let cool slightly on a rack.
In a bowl, whip the cream with the confectioners' sugar and fold in the remaining 1/4 cup of orange puree.
Brush the melted jam over the warm cake and let cool. Unmold the cake and serve with the orange whipped cream.