• 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, lemon extract, and lemon zest until smooth.
• Sift the all-purpose flour, powdered sugar, and baking powder on top of the wet ingredients.
• Stir gently until just combined, being careful not to overmix.
• Pour the batter into the prepared cake pan and smooth the top with a spatula.
• Bake for 35 to 40 minutes, or until a toothpick inserted into the center comes out clean.
• Allow the cake to cool in the pan on a cooling rack for 1 hour before attempting to remove it.
• Let the cake cool completely before applying icing.
• To make the icing, sift the powdered sugar into a medium bowl.
• Gradually add fresh lemon juice, stirring constantly, until the icing reaches a spreadable consistency that clings to the back of a spoon.
• Spread the icing evenly over the cooled cake using a spatula.
• Chill the cake before serving for best results.

Variation:

For a layered version:

• Double the cake recipe and bake in two separate pans.
• Use the Cream Cheese Frosting from Pumpkin Cupcakes (adjusted with lemon flavor: replace vanilla extract with half the amount of lemon extract or add 2 teaspoons of lemon zest).
• Apply frosting between the layers, then cover the top and sides with the remaining frosting.