Preheat the oven to 350°F
Line an 8 inch metal baking pan with parchment paper, I like it to go up and over the sides for easy removal.
In a medium bowl, whisk together the all purpose flour, baking powder, cinnamon, and kosher salt until well combined.
In a separate large bowl using a handheld or stand mixer on medium speed, beat the butter and sugar until light and fluffy, about 3-4 minutes.
Add the eggs one at a time, beating after each until smooth, add the vanilla and instant coffee, mix well.
Make sure to scrape down the bowl as needed, get the bottom really well.
In two batches, gradually add the dry ingredients to the butter mixture, alternating with the buttermilk until combined, do not over mix.
Pour the batter into the prepared cake pan and smooth the top with a spatula. Top evenly with the crumble, making sure it's an even layer.
Position it on the center rack of the oven to ensure even baking, avoiding placement too close to the top or bottom. Bake for 28-32 minutes, or until a toothpick inserted into the center comes out clean and the top is golden. Try not to over bake, keep an eye on it!