Preheat the oven to 350 degrees.
Start the blood orange simple syrup by stirring together the ½ cup blood orange juice and ½ cup granulated sugar in a small saucepan over medium heat. Cook for about 5 minutes until the sugar is dissolved. Increase the heat and simmer for another 5 minutes. Pour the simple syrup in a heat-safe container and cover with plastic wrap. Set aside and let cool to room temperature.
½ cup blood orange juice, ½ cup granulated sugar
Meanwhile, in a bowl, whisk together the 2 ½ cups cake flour, 2 tsp baking powder, ½ tsp baking soda, and 1 tsp salt. Set aside.
2 ½ cups cake flour, 2 tsp baking powder, ½ tsp baking soda, 1 tsp salt
Add the 3 eggs and 1 ¼ cup granulated sugar to the bowl of an electric mixer fitted with a paddle attachment. Beat on medium-high speed for about 5 minutes until light and silky. Add the 1 ½ tsp almond extract and stir to combine. On medium speed, slowly stream in the 1 ½ cups olive oil into the egg mixture. Mix for 2 minutes.
1 ¼ cup granulated sugar, 3 eggs, 1 ½ cups olive oil, 1 ½ tsp almond extract
Add the dry ingredients to the mixer and beat just to combine, about 1 minutes. Stir in the 2 tbsp orange juice and 1 ½ tbsp orange zest.
1 ½ tbsp orange zest, 2 tbsp orange juice
Line the bottom of a spring-form pan with parchment paper. Pour the simple syrup into the pan and spread into an even layer. Place the blood orange slices on top of the simply syrup later in a single layer.
2 blood oranges
Pour the batter over top of the simple syrup and orange slices and spread into an even layer.
Bake the cake for 40-45 minutes until a toothpick comes out clean. Let cool in the pan until room temperature before releasing from the springform pan and flipping to reveal the oranges on top.