Preheat oven to 350 degrees. Butter a 9-inch round cake pan and line with parchment paper; butter paper. In a small saucepan, combine 2/3 cup sugar, water, and 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 remaining 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 mixture 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 to 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. Serve with yogurt and remaining syrup.
If you'd like to omit the semolina, increase the all-purpose flour to 1 1/2 cups. Instead of orange zest, you can substitute lemon zest: 2 teaspoons grated and 4 strips.