Heat oven to 425 degrees F.
Lightly butter an 8-inch square baking pan
. Line pan with parchment paper or foil, extending over sides by 2 inches; set aside.
On a separate baking sheet
toast almonds 4 minutes until lightly browned, remove from heat, cool, chop, and set aside.
For the crust: In a small mixing bowl
, combine soy flour
, baking powder, 3 tablespoons softened butter, cream cheese, and sour cream. With an electric mixer on low, beat just until combined.
Form into a ball, then press into a 4-inch disc. Wrap well in plastic and chill 20 minutes.
Using fingers, press dough in an even layer over the bottom of prepared pan. Sprinkle 1/4 cup almonds (reserve 1 teaspoon for the meringue topping) over top and press firmly into dough.
Using a fork, prick dough in several places. Loosely cover pan with foil; bake 10 minutes.
Reduce oven temperature to 375 degrees F and continue to bake until crust is browned, about 15 minutes more. Cool on a wire rack.
Reduce oven temperature to 325 degrees F
For the lemon filling: In a 1-1/2 -quart heavy saucepan, combine egg, egg yolks, and 2 tablespoons granular sugar substitute. Stir in lemon zest and lemon juice. Cook over medium-low heat, stirring constantly, just until the mixture thickens, 4 to 6 minutes. Do not overcook
Remove from heat and add 1 tablespoon softened butter. Whisk until blended and smooth.
Pour into a small bowl, place plastic wrap directly on surface of filling and refrigerate until chilled, about 30 minutes.
For the meringue: In a large mixing bowl
, with an electric mixer on medium, beat egg whites until frothy. Add cream of tartar. Increase speed to medium-high and beat just until egg whites form stiff peaks, about 2 minutes.
Beat in 3 tablespoons granular sugar substitute, 1 tablespoon at a time, scraping down sides of bowl once or twice. Add vanilla. Beat until thick, about 30-45 seconds.
To assemble: Evenly spread lemon filling over baked crust. Drop mounds of meringue over filling. Using the back of a spoon, quickly spread meringue, completely covering lemon filling.
Bake until meringue is golden brown, 15-18 minutes. Cool on wire rack. Run knife along unlined sides of pan and, holding extended ends of parchment, carefully lift out of pan
Cut into 9 squares. Chill until ready to serve. (If assembling completely, squares must be served on the day prepared. Can be refrigerated up to 3 hours; see note below for making ahead.)
Sprinkle meringue squares with remaining 1 teaspoon of almonds before serving.
Fat, total (g)
Percent Daily Values are based on a 2,000 calorie diet