Preheat oven to 350 degrees F.
Grease and flour a 9-inch springform pan.
In a medium-sized bowl, sift together the all-purpose flour, almond flour, baking powder and salt. Set aside.
In the bowl of a stand mixer or handheld mixer fitted with the whisk attachment, beat the eggs and granulated sugar until thick and pale yellow in colour. For about 3 minutes.
Mix in the olive oil, milk, vanilla and almond extracts, zest and thyme until well incorporated.
Switch to the paddle attachment and mix in the flour mixture until well combined.
Fold in 1 cup of the grapes with a rubber spatula. (Toss the grapes with a little flour beforehand and shake off any excess.) This avoids the grapes from sinking to the bottom.
Transfer the cake batter to the prepared pan and level off with the back of a spoon.
Scatter the remaining 1 cup of grapes evenly over the top of the cake.
Sprinkle the top of the cake with sliced almonds.
Bake the cake in a preheated oven for about 40 minutes.
When ready, the cake will have a deep golden brown colour and spring back to the touch. Or, if a toothpick inserted inside comes out clean, then it's ready.
Remove the cake from the oven and transfer it to a cooling rack.
Run a knife alongside the edges of the pan and allow it to cool for 30 minutes.
Release the cake from the springform pan and cool completely before dusting with powdered sugar.
Garnish with sugared grapes or fresh thyme leaves if desired. (see notes below on how to make sugared grapes)