Preheat oven to 375
In a stand mixer, combine the butter and sugar and mix on medium high speed for 3-4 minutes until light and fluffy. Add the eggs, one at a time, scraping down the sides in between additions.
In a small bowl, sift together the flour, baking powder and salt. Add the dry ingredients into the mixer and mix for 30-60 seconds until just combined. Add the almond milk, lemon extract and orange zest and stir to combine.
Spray a 9 inch springform pan with baking spray. Transfer the batter into the pan and transfer to the oven and bake for 37-40 minutes. When done, remove from oven and let cool before removing from the springform pan.
Thinly sliced citrus and poke out any seeds. Prepare a medium-size bowl with ice and water.
Bring a pot of water to boil, add lemon slices and boil for one minute. remove slices from boiling water and plunge into ice water for a couple of minutes until cool, then drain.
In a medium-size skillet bring sugar and water to a simmer, stirring occasionally until sugar is dissolved. Add citrus slices in a single layer and simmer for about an hour, until rinds are translucent. Remove citrus slices and cool on wire rack. Reserve some of the cooking liquid to drizzle over the cake once done baking.