Preheat oven to 350 degrees. Spray a 9-inch springform pan with cooking spray. Line the bottom of the pan with a piece of parchment paper cut to fit and lightly spray the paper.
In a small saucepan, combine the honey and ginger and bring to a low simmer. Let simmer for 5 minutes. Remove from heat and let cool. When cooled, remove and discard the ginger.
In the bowl of an electric mixer, combine the egg yolks, vanilla, salt, and baking soda, and ½ cup of the cooled ginger honey. Beat at high speed for 5 minutes or until light yellow and fluffy. Beat in the almond flour until combined. Scrape the sides and bottom of the mixing bowl to make sure everything is fully combined.
In a clean bowl with clean beaters, combine the egg whites with the cream of tartar. Beat on high speed until stiff peaks form. Stir 1/3 of the beaten egg whites into the almond mixture, stirring well to incorporate. Gently fold in half the remaining egg whites, being careful not to deflate the whites. Repeat with the remaining egg whites.
Pour into the prepared pan and scatter the sliced almonds on top. Bake for 35 – 40 minutes or until a toothpick inserted into the center comes out clean. Immediately brush the top of the cake with the remaining ginger honey. Let the cake cool completely in the pan then remove the outer ring of the springform pan.