Preheat the oven to 350 degrees F (175 degrees C). Grease an 8-inch round cake pan with olive oil and line the bottom with a round of parchment paper.
Add Fennel Seeds (1 teaspoon) to a mortar and pestle with Granulated Sugar (1 tablespoon) and grind until fine.
Sift together the All-Purpose Flour (1 1/4 cup), Baking Powder (1/2 teaspoon), Salt (1/4 teaspoon), and fennel sugar. Add Almond Flour (1/2 cup) and whisk well, set aside.
Whisk the Egg (2) and the Granulated Sugar (3/4 cup) in a medium bowl until fluffy and light in color, about 2 minutes. Slowly stream in the Extra-Virgin Olive Oil (1/2 cup) oil while continuing to whisk until all of the olive oil is incorporated well.
Add the dry ingredients alternately with the Vanilla Extract (1 tablespoon) and Greek Yogurt (1/2 cup). Mixing until just blended.
Pour the batter into the prepared pan and spread the batter out evenly with a spatula. Rap the pan on the counter 4 or 5 times to remove any pockets of air in the batter.
Bake the cake in the center of the oven, until a toothpick inserted comes out clean, approximately 22-25 minutes.
Remove the cake from the oven and allow to cool for 10 minutes on a wire rack. Remove the cake from their pans. Allow to cool completely on the rack before icing.
Preheat oven to 400 degrees F (205 degrees C).
Add the Grapes (1 pound) to a baking pan, drizzle with Olive Oil (1 tablespoon) and sprinkle with Fennel Seeds (1 teaspoon).
Roast for 15-20 minutes until the grapes have just started to release their juices and the skins have began to wrinkle
Remove grapes from the oven and allow to cool to room temperature before assembling the cake
Sift the Powdered Confectioners Sugar (1 cup) into a medium bowl, add the Greek Yogurt (2 tablespoon) and whisk until smooth. The glaze should be thick but spreadable.
Once the cake and the roasted grapes have fully cooled, spoon the glaze over the cake. You can pre-slice the cake and glaze the individual slices - this allows for the neatest presentation.
Allow the glaze to air dry for about 15 minutes before arranging the grapes on top of the cake. Garnish with young wild fennel seeds if you have access to them and serve.