Preheat the oven to 350°F.
Grease and line two 5-inch cake pans with coconut oil and parchment paper cut into rounds for base of pans.
In a small bowl or a 2-cup liquid measuring cup, whisk together almond milk, canola oil, golden syrup, apple cider vinegar, lemon extract, vanilla extract, and lemon zest until combined well.
In a large bowl, sift together the flour, salt, baking powder, and baking soda.
Add the liquid mixture to dry ingredients. Whisk together gently, mixing until just combined and very few lumps remain - it's okay if some remain. Divide the cake mixture between the two 5-inch pans evenly.
Place in the oven to bake for about 25-30 minutes. Insert a knife in the middle of the cakes to check if they are finished. If the knife comes out clean, they're done. Allow to cool for 15 minutes before removing cakes from the pans. Wrap the cakes with cling film and place in the fridge overnight. If you plan on making the cake further in advance, you can freeze the layers and defrost them when you're ready to assemble the cake.
To make the frosting: Cream the butter with vanilla extract in a standup food mixer or a medium bowl. Add sifted powdered sugar and almond milk, and mix together well. Cover with cling film and place in fridge for at least 2 hours.
Remove frosting from the fridge. If the frosting is too stiff, mix in a splash of almond milk. It should have a pliable consistency - not too stiff, but not runny.
Remove cakes from the fridge. Level each cake layer by cutting the tops with a serrated knife. With the bottom facing up, place one of the cakes onto a cake board (or plate) with a little frosting underneath to help it stick.
Generously spoon some of the jam on top of the cake layer and spread it out, but be sure to leave a 1" space on the edge of the cake. This prevents the jam from seeping out when you stack the cake layers. Use a pallet knife to apply frosting on the outer edge of the top of the cake, around the outside the jam. Place the other cake layer onto a flat surface, bottom facing up. Use a pallet knife to apply frosting on the top of the cake, covering the surface and smoothing it out. Carefully place the cake on top of the other so that the jam and frosting meet together in the middle.
Once stacked, use the pallet knife to frost the entire cake. Use the pallet knife to achieve the naked cake icing effect, vertically scraping the frosting off to get rid of excess frosting. Continue all the way around, scraping excess frosting into a separate bowl. Add fresh strawberries (optional) as a fruit topping.