Put first four ingredients into a heavy-bottomed sauce pan and bring to a boil. Reduce heat to medium and cook for about 5 minutes. In a small bowl mix cornstarch and water to combine. Stir the cornstarch mixture into the strawberries and continue cooking another minute or so until mixture thickens. It will continue to thicken after it cools. Remove from heat and cool. Refrigerate until you are ready to use.
Heat oven to 350 degrees. Lightly butter two round 9" cake pans. Line each pan with a circle of parchment paper.
Using a mixer, beat eggs and sugar together at medium speed for 1 minute. Add remaining flour blend, baking powder, xanthan gum, oil, milk, vanilla, lemon extract and lemon zest and beat for another minute to combined the ingredients.
Pour half of the cake batter into each pan and bake in the center of the oven for about 35 minutes. Cake is done when a toothpick inserted in the center comes out clean. Cool the cake pans on racks until room temperature. Tip: Before removing the cake from the pans put them in the freezer for half an hour or overnight. This will help set up the cake and make it easier to frost without crumbling.
While the cake is baking, make the frosting. Using a mixer, combine cream cheese, sugar, lemon zest, lemon extract, and vanilla paste and mix until smooth. Slowly add the whipped cream as you whip the frosting until frosting holds stiff peaks.
When the cake has thoroughly cooled. Use a knife or spatula to release the edges of the cake. Place your serving plate over one of the cakes and invert it. When the cake releases, peel back the parchment paper. The cake should be bottom-side up.
Spread the strawberry filling over the top of the first layer. Cover the strawberry filling with a layer of the whipped cream frosting. Remove the second cake from the pan by inverting it into your hand. Peel off the paper and gently lay the second layer on top of the first layer. Frost the top of the cake with cream cheese frosting, and then the sides of the cake with cream cheese frosting. If any of the filling oozes out between the layers, like it did for us, no worries. Spread the oozing filling along with the frosting and you will get variegated pink and white on the sides of the cake. If you want all white sides, don't spread the filling too close to the edges. We liked the variegated color.
Slice the remaining strawberries and arrange them on top of the cake.
Recipe by Something New For Dinner at https://somethingnewfordinner.com/recipe/strawberry-lemon-gluten-free-birthday-cake/