In a large bowl, whisk together the flour, baking powder, salt, cinnamon, nutmeg, and baking soda.
With a hand mixer cream butter and sugar on medium speed until fluffy, about 3 minutes.
Add eggs and vanilla and mix until fully combined.
In alternate batches, add dry ingredients and buttermilk, mixing until just combined.
Fold in pears with a rubber spatula, scraping sides and bottom of mixing bowl. Transfer batter into the greased and floured 25 cm Bundt cake pan (or a silicone one).
Bake in the oven for 50-55 minutes at 160C, or until a skewer inserted into center of cake comes out clean. Remove from oven and place pan on cooling rack.
Using a wooden skewer, poke holes in the cake while it's still warm. Carefully pour the brown butter glaze over cake, making sure it gets in all of the holes. Let cake cool completely before removing from pan.
When cake is inverted and placed on its serving plate, drizzle as much or as little caramel sauce as you'd like.
In a small saucepan over medium-low heat, combine the butter, sugars, and vanilla. Cook until fully melted and allow to brown, being careful not to let the mixture boil.
In a medium saucepan over medium heat, combine sugar and water. Stirring constantly with a rubber spatula, heat until clumps form and then melt into thick, amber-colored liquid, being careful not to burn it.
Carefully stir in the butter until it's melted, 2-3 minutes. Then very slowly drizzle in the heavy cream while stirring. The mixture will bubble and possibly splatter, so be careful. Allow it to boil for 1 minute, then remove from the heat and stir in the vanilla extract. Allow to cool, and reheat as necessary.