For the blueberry tart, preheat the oven to 160 °C (top and bottom heat) degrees. Coat the cake tin with Kronenöl Spezial with fine butter flavor and dust with flour.Separate the eggs. Sift flour and baking powder and mix with grated almonds. Beat the egg yolks, powdered sugar, salt, vanilla sugar and grated lemon peel until foamy (at least 10 minutes).Slowly pour in the special crown oil with fine butter flavor. Add cold orange juice and flour mixture alternately, stirring constantly. Beat egg whites well, add granulated sugar, beat until creamy and gently fold into the mixture. Pour into the cake tin, smooth out and bake for approx. 45 minutes on the middle shelf. Remove the cake from the oven and allow to cool. Cut the cake twice horizontally and place part of the base in the cake tin.For the cream, whip the whipped cream and chill. Soak the gelatine in cold water. Warm blueberries and powdered sugar slightly and puree finely with a hand blender. Add sour cream and blend until smooth. Heat the lemon juice, dissolve the gelatine in it, pour it into the blueberry mixture and mix everything together. Fold in the whipped cream and fill and garnish the blueberry tart with it. Chill the cake for 5 hours, remove from the mold and cover with blueberries and rose petals.