Preheat oven to 350°F. Lightly butter the sides of an 8-inch round springform pan and dust with flour, tapping out the excess. Line the base with a round of parchment paper.
Combine butter, maple sugar, granulated sugar and vanilla in a large mixing bowl and beat with an electric hand mixer for 2 minutes until pale and fluffy. Beat in eggs one at a time until the mixture is smooth. Add maple syrup and mix until creamy.
Sift together flour, baking powder, baking soda and salt in a separate large bowl. Add oats and stir to combine. Add half of this flour mixture to the butter mixture and start mixing on low speed until mostly incorporated. Add the yogurt and mix until smooth. Fold in the remaining flour mixture by hand until just combined.
Spread the thick batter into the prepared pan making a slight depression in the center using the back of a spatula so that it is slightly higher around the edges. Scatter blueberries evenly all over the surface and bake for 45-50 minutes until a skewer inserted into the center comes out clean. If using frozen berries, bake closer to 50 minutes. Makes 8-10 servings.
If using frozen blueberries, pull them from the freezer for 10-15 minutes to take the chill off so that the batter bakes evenly.