Place egg whites in a large bowl; let stand at room temperature for 30 minutes. Beat egg whites on medium speed until foamy. Add cream of tartar; beat until soft peaks form. Gradually add 1-1/4 cups sugar, 1 tablespoon at a time, beating on high until stiff peaks form. Sprinkle cornstarch over egg white mixture; fold in. Fold in lemon juice and extract.
Coat a 14-in. pizza pan with cooking spray. Spoon meringue onto pan, forming a 12-in. heart; build up edges slightly. Bake at 250° for 45-55 minutes or until crisp. Cool on pan on a wire rack.
In a bowl, beat cream until soft peaks form. Gradually add the remaining sugar, beating until stiff peaks form. Spoon over meringue; arrange strawberries over top. Serve immediately.