Preheat oven to 350F. Spray 9 inch springform pan with pam or buttter it. Set the pan on a foil-lined baking sheet to catch any drips while baking
In a medium bowl, mix graham cracker crumbs, 1.5 tbsp sugar, melted butter, and cinnamon until homogeneous. Press crumbs into bottom of springform pan and about 1/3 of the way up the sides
Bake crust until light brown, 10-12 minutes. Remove from oven
In a stand mixer with paddle attachment (or by hand, or in food processor), beat cream cheese with 150 g sugar until smooth. Add eggs one at a time, stopping between each addition to scrape the sides. Add 280 g dulce de leche, vanilla, and salt. Scrape the batter into the springform pan
Bake for ~55 minutes, until cheesecake is just set in the center. If you jiggle the pan, the outer part of the cake should not move, but a small circle in the middle, about the size of a bracelet, should still quiver
Remove the cheesecake from the oven. Set on a cooling rack. Run a knife around the outside of the cake to loosen it from the pan, then let the cheesecake cool completely
When cake is cooled, remove sides of springform pan
Warm 195 g dulce de leche and cream or milk in a saucepan over low heat (or microwave). Stir until smooth. Spread over the top of the cheesecake, pushing it to the edges and over the edges for added decor
Just before serving, sprinkle with flaky salt, just enough so each bite of cake has a flake or two