For cake: In bowl, sift ¾ cup of the sugar with the flour; in large bowl, beat egg whites until soft peaks form; beat in almond extract and remaining sugar, 2 tblsps at a time, until stiff and glossy peaks form; sift flour mixture over top, ¼ at a time, gently folding in after each addition; fold in chopped pecans; scrape into ungreased 10-inch (4L) tube pan; run spatula through batter to eliminate any large air pockets; smooth top.
Bake in centre of preheated 350F (180C) oven until top springs back when lightly touched, 45-60 minutes; invert pan; let stand on legs attached to pan, or set on bottle or funnel, until cooled completely.
For caramel sauce: In saucepan, bring butter and half of cream to boil; add sugar and remaining cream; return to boil; reduce heat and simmer for 5 minutes; remove from heat; set aside to cool to room temperature.
Remove cake from pan; cut into 3 layers; in large bowl, whip cream, icing sugar and vanilla; place bottom cake layer, cut side up, on flat cake plate; using piping bag fitted with star tip, fill hole of cake with whipped cream mixture; pipe border on top around edge; pour ¼ cup (50mL) of the caramel sauce inside border; repeat layers once; top with remaining cake layer, cut side down.
Spread 3 cups (750mL) of the cream mixture over top and side; pipe rosette in centre; pipe border around edge; spread thin layer of caramel sauce inside border; garnish with pecan halves.