Preheat oven to 250 degrees. Place whole citrus in a pot with enough water to cover the fruit. Bring to a boil, then lower the heat and simmer for 30 minutes to soften the fruit.
While the fruit is at a simmer, place almonds on a baking sheet and toast in the oven for 20 minutes.
Remove almonds and allow to cool.
Turn oven to 350 Degrees.
Add cooled almonds to food processor and pulse until they reach a sandy texture. Add flour and baking powder to the processor. Pulse to combine. Pour in a separate bowl.
After citrus has simmered, pour out the water and let cool to room temperature. Cut fruit in 1/4 and remove seeds. Place fruit, with skin, in a food processor and puree until smooth. While processing, slowly pour in olive oil to make a paste.
In a bowl, whisk eggs with salt until foamy, then add sugar a little at a time while whisking until dissolved.
Fold in orange paste. Then fold in flour mixture. Do not over mix. Pour into a 10” springform pan. (I used an angel food cake pan). Bake for 45 minutes to one hour, until a toothpick inserted in the center of the cake comes out clean. Remove from oven and let cool on a wire rack until the sides pull away.
Dust with powdered sugar if desired.