• Preheat the oven to 350°F (180°C, or gas mark 4).
• Lightly coat an 8-inch (20-cm) round cake pan with nonstick cooking spray.
• In a large bowl, whisk together the yogurt, canola oil, vanilla extract, and chocolate extract (if using).
• Sift the flour, powdered sugar, cocoa powder, baking powder, and salt over the wet ingredients.
• Stir until just combined, being careful not to overmix.
• Pour the batter into the prepared pan, spreading it evenly.
• Bake for 35 to 40 minutes, or until a toothpick inserted into the center comes out clean.
• Let the cake cool in the pan on a cooling rack for 1 hour before removing.
• For the best texture, chill the cake overnight before serving.

Sacher Torte Variation:

• Double the cake recipe and bake in two separate 8-inch (20-cm) round cake pans.
• Spread ¼ to ½ cup (80 to 160 g) all-fruit raspberry jam evenly over one of the cakes, then place the second cake on top.
• Double the Chocolate Ganache recipe (see page 74) or prepare a single recipe of Chocolate Agave Frosting (see page 447).
• Spread the frosting or ganache over the top and sides of the layered cake.
• Let the cake cool for several hours before serving.
• For optimal flavor, prepare the cake a day in advance.