Preheat oven to 375°F (190°C). Toss peach slices with melted butter and arrange in a single layer on a baking sheet. Roast for 15-18 minutes until softened and lightly caramelized. Let cool, then divide among four 6-ounce ramekins.

Reduce oven temperature to 325°F (165°C). In a medium saucepan, combine heavy cream, vanilla bean seeds and pod (or vanilla extract), and a pinch of salt. Heat over medium until small bubbles form around the edges, then remove from heat and let steep for 10 minutes.

In a mixing bowl, whisk egg yolks and 1/3 cup sugar until pale and slightly thickened, about 1 minute. Remove vanilla pod from cream, then slowly pour warm cream into yolks while whisking constantly to temper the eggs.

Strain custard mixture through a fine-mesh sieve into a large measuring cup or pitcher. Gently pour custard over the roasted peaches in each ramekin, filling nearly to the rim.

Place ramekins in a deep baking dish and carefully pour hot water into the dish until it reaches halfway up the sides of the ramekins. Bake for 35-40 minutes until edges are set but centers still jiggle slightly when shaken.

Remove ramekins from water bath and let cool to room temperature, about 1 hour. Cover with plastic wrap and refrigerate for at least 4 hours or up to 2 days.

Just before serving, blot any moisture from the custard surface with a paper towel. Sprinkle 1-1.5 teaspoons of sugar evenly over each custard. Using a kitchen torch, caramelize the sugar in circular motions until deep golden brown and glassy. Let set for 1-2 minutes before serving.