Preheat oven to 350ºF (180ºC). Grease a 9 x 13-in. (3 L) baking pan and use a couple tablespoons of the flour to dust the pan; shake out excess. In bowl, stir rest of the flour with baking powder and salt. Set aside.
In a separate bowl, beat butter and sugar using electric mixer on medium speed for about 2 min., until light and fluffy. Beat in eggs one at a time, incorporating each fully before adding next one. Beat in vanilla.
With the mixer on low, alternately add the dry mixture in 3 parts with the milk in 2 parts, starting and ending with the dry mixture. Scrape the bowl as needed between additions.
Scrape batter into prepared pan, smoothing the top. Bake 30 to 35 min. or until a tester comes out clean when inserted into centre of cake. Let stand 10 min. before turning cake onto wire rack to cool completely.
Just before serving, beat cream with icing sugar until stiff peaks form. Spread evenly on top and sides of cake.
Cut raspberries in half lengthwise. Overlapping slightly, arrange 1/2 the raspberries, cut-side down, in the shape of a maple leaf in the centre of the cake. Tip: To avoid spaces between raspberries, slightly overlap the berry edges. Arrange remaining raspberry halves in three rows on each side of maple leaf. Serve immediately.
The unfrosted cake can be made 1 day ahead and stored in an airtight container, or it can be wrapped tightly and frozen for up to 2 weeks before thawing and decorating.