Preheat the oven to 325°F (160°C) and wrap a 9-inch springform pan with heavy-duty aluminum foil on the outside.

In a mixing bowl, combine graham cracker crumbs, granulated sugar, melted butter, and sea salt; stir until mixture resembles wet sand, then press firmly into the bottom of the prepared pan.

Peel and mash or blend bananas until smooth, then strain through a fine-mesh sieve if excess liquid is present; set aside ripe banana puree.

Beat the softened cream cheese in a large bowl on medium speed for 2 to 3 minutes until smooth and creamy, scraping down the sides halfway through.

With the mixer on low speed, gradually add granulated sugar and light brown sugar until combined; then pour in the banana puree and mix until just incorporated.

Add eggs one at a time, mixing on low speed and scraping the bowl after each addition; then mix in sour cream, cornstarch, vanilla extract, banana extract, nutmeg, and salt until no streaks remain.

Pour the filling over the crust and smooth the top with a rubber spatula; tap the pan gently on the counter to release any air bubbles.

Place the springform pan in a larger roasting pan and add hot water to the roasting pan until it reaches halfway up the sides of the cheesecake; bake for 50 to 60 minutes until the edges are set and the center jiggles slightly.

Turn off the oven and crack the door open 4 inches; let the cheesecake cool in the oven for 15 minutes, then remove from the water bath and cool completely on a rack for 1 hour; refrigerate for at least 3 hours or overnight before serving.