Sift flour, baking powder, baking soda and salt together.
In the top of a double boiler, melt margarine and baking chocolate; blend in sugar replacement.
Remove from heat.
Beat in eggs, pineapple and almond extract.
Stir in flour mixture until well blended.
Fold in walnuts.
Pour into a greased 8 in. (20 cm) sq. pan.
Bake at 350°F (175°C) for 30 to 35 minutes.
Cool and cut into 1 x 2 in. (2.5 x 5 cm) bars.