Heat the oven to 180 C / 350 F. Butter a 23 cm / 9-inch baking dish or pie dish with the 1 tbsp butter.
Peel, core, and slice the pears into 5 mm thick pieces. Arrange them in a single layer in the prepared dish, overlapping slightly.
Whisk the eggs and 60 g sugar together in a mixing bowl until pale and slightly thickened, about 1 minute.
Whisk in the flour and salt until no lumps remain. Add the milk and vanilla extract, whisking until the batter is smooth and pourable, or blitz everything in a blender for 10 seconds.
Pour the batter over the pears, letting it settle into the gaps between slices.
Sprinkle the remaining 1 tbsp sugar evenly over the top.
Bake for 35 to 40 minutes, until puffed and golden brown, with a slight jiggle left in the center when you nudge the dish.
Cool in the dish on a rack for at least 10 minutes. It will sink in the middle as it cools, which is normal.
Dust with powdered sugar and serve warm or at room temperature.