Preheat oven to 350°F.
Pour melted butter into a 9x13 baking dish — no need to grease.
Toss drained peaches with bourbon, ½ cup brown sugar, cinnamon, nutmeg, and ginger. Let sit 5–10 minutes to release some of their own juices.
In another bowl, whisk flour, granulated sugar, milk, and vanilla until just combined (a few lumps are fine).
Pour batter over the melted butter — do not stir.
Spoon peach mixture over batter.
Whatever juices are left at the bottom of the bowl after spooning the peaches, add enough of the reserved peach liquid from the cans to make the total ½ cup.
Drizzle the combined juices over the peaches.
Toss pecans with 1 tbsp melted butter + 1 tbsp brown sugar; sprinkle on top.
Bake 40–50 minutes, until golden and bubbly.
Cool slightly; serve warm with ice cream.