Pear Upside-Down Cake

Boil syrup without stirring, occasionally swirling pan and brushing down sides with a wet pastry brush, until sugar turns dark amber, 8-10 minutes.

Remove pan from heat; add 1 tablespoon butter (caramel will bubble vigorously) and whisk until smooth.

Pour caramel into prepared cake pan and swirl to coat bottom.

Peel, halve, and core the pears.

Place flat on a work surface and cut lengthwise into 1/8"-thick slices.

Layer slices over caramel, flat side down, overlapping as needed.

Mix remaining 3/4 cup sugar, 8 tablespoons butter, and vanilla in a large bowl.

Using an electric mixer, beat on medium speed until light and fluffy, about 3 minutes.

Add yolks one at a time, beating to blend between additions and occasionally scraping bowl.

Beat in flour mixture in 3 additions, alternating with milk in 2 additions, beginning and ending with flour mixture.

Using clean, dry beaters, beat egg whites on low speed in a medium bowl until frothy.

Increase the speed to medium and continue to beat until whites form soft peaks.

Fold about 1/4 of the whites into cake batter.

Add in remaining whites; gently fold just to blend.

Pour batter over pears in pan; smooth top.

Bake cake, rotating pan halfway through, until top is golden brown and a tester inserted into the center comes out with a few small moist crumbs attached, about 1 hour.

Let cool in pan on a wire rack for 30 minutes.

Run a thin knife around inside of pan to release cake.

DO AHEAD: Can be made 1 day ahead.

Store airtight at room temperature.

Invert cake onto a plate; remove parchment paper.

Serve warm or at room temperature with whipped cream or caramel gelato, if desired.