Preheat oven to 350ºF.
Line the bottom of a spring form pan with parchment and spray pan with cooking spray.
Soak saffron in 2 tablespoons of warm water.
In a bowl, mix almond flour, orange zest, cardamom, and baking powder. Set aside.
In a large bowl, whisk egg whites until frothy. Slowly add the xylitol while whisking. Add the rose water, salt, and cream of tarter. Whisk until the mixture is thick and white with soft peaks.
Add the dry ingredients into the meringue in 3 stages. Fold into the meringue making sure the dry mix is fully incorporated before adding more. Do not over mix or you will deflate the egg whites.
Add the saffron with the water to the batter. Folding in slowly.
Pour the batter into a springform pan and top with sliced almonds.
Bake for 40 minutes.
Remove from oven and let cool. The sides will pull away from the pan and will be light and fluffy.