In a large mixing bowl, add the flour, salt, granulated sugar, baking powder, baking soda, buttermilk (or sour milk), eggs and vanilla. Mix with an electric mixer until well combined. Scrape down the sides of the bowl and mix again, just until all ingredients are incorporated.
Turn the mixer on medium and slowly add in the melted butter. Mix only until the ingredients are well combined. Don't mix for several minutes here as that will make the cake dense.
Pour the batter into the greased 9x13 inch pan and set it aside while you make the crumb topping.
For the cinnamon swirl:
Mix all the topping ingredients together very well. Depending on how soft the butter is, you may need to use a mixer. Sprinkle (or drop) the mixture over the cake and swirl the cinnamon mixture and batter with a knife to marble.
Bake in the oven at 350 degrees Farenheight for approximately 30-35 minutes. Let the cake sit on a rack for about 20 minutes before adding the glaze.
For the glaze:
Mix all the glaze ingredients together. Once the cake is fully baked and cooled for about 20 minutes , drizzle the glaze over it. Serve the cake warm.
*If you don't have buttermilk, you can make sour milk as a substitution: Pour 1 ½ cup of milk into a cup or bowl. Take out 1 ½ tablespoon of the milk and replace it with 1 ½ tablespoon of vinegar or lemon juice. Mix together and let it sit for a couple of minutes before adding to the batter.This cake is best eaten warm. Store leftovers well covered in the fridge and heat for a bit in the microwave to warm up slices.Nutritional values are an estimate. Make sure to check out the TIPS & FAQs for this recipe in the blog post, which may answer questions about substitutions.*This recipe card may contain affiliate links. As an Amazon Associate, I earn from qualifying purchases.