Preheat oven to 350 F/180 C. Butter a 9-inch
(23 cm) round cake pan and line with
parchment paper; butter paper.
In a small saucepan, combine 2/3 cup (75 g.) sugar,
½ cup (120 ml.) water and wide orange
zest strips.
Bring to a simmer over medium
high; cook until sugar has dissolved, about 3
minutes. Set syrup aside to steep.
In a large bowl, whisk together flours, almonds, grated orange zest, baking powder, and salt. In another large bowl,
using an electric mixer, beat butter and 1 cup (300 g) sugar until light and creamy.
Add eggs, one at a time, beating well after each addition. Beat in vanilla. With mixer on low, alternately beat in flour mixtures and yogurt, beginning and ending with flour
mixture.
Transfer batter to prepared pan; bake until cake is golden and a toothpick inserted in center comes out clean, 50-55 minutes.
Let cool in pan 10 minutes, then invert onto a rimmed serving plate.
Using a fork, poke shallow holes (about 15) into top of cake. Pour half the syrup over cake; garnish with orange-zest strips from syrup. Let cool completely.