In a large bowl, sift or whisk together flour, salt, baking powder, baking soda, sugar, and cocoa. Add 1 cup and 2 tablespoons of pineapple juice and 1 cup and 2 tablespoons of canola oil. Mix for 1 minute.
Add eggs, 3/4 cup of pineapple juice and the vanilla. Mix 5-6 minutes with a whisk, 3-4 minutes with a hand mixer.
Pour into pans, bake, test by placing and removing a toothpick through the center at 25 minutes. When toothpick comes out clean, loosen from pans and then put back in the pans. Let cakes cool for 15 minutes. Keep in the pans, wrap in foil, and put in the freezer for at least 2 hours.
Place first two ingredients into medium saucepan and heat over medium heat until brown sugar is dissolved. Put mixture into food processor or blender and blend until smooth.
Mix together cornstarch and water.
Place salsa mixture back on heat. Bring to a slow boil. Whisk constantly while adding cornstarch mixture to avoid lumps.
Glaze should coat the back of a spoon with only a slight drip.
Bring cakes out of the freezer and pour pineapple glaze over the top of each layer, stacking each layer on top of the previous layer.