In a large bowl, whisk dry ingredients together. In a second bowl, whisk milk, eggs, and vanilla until combined. Add about two-thirds of the wet ingredients to the dry mix and whisk until incorporated. Add remaining wet ingredients and whisk until no lumps of flour remain.
In a 10-inch cast-iron skillet, melt butter over medium heat. Pour in batter and place skillet in a cold oven. Turn the heat to 400°F and bake for 35 minutes, until golden and puffy.
While the Dutch baby bakes, prepare the pear topping. Mix sour cream and heavy cream in a small bowl and set aside.
Add butter to a hot skillet over medium heat. Once butter melts, add sliced pears and brown sugar. Sauté, stirring occasionally, until pears begin to caramelize, about 5–7 minutes. Sprinkle with spices and stir gently. Sauté for about 1 minute more, remove from heat, and set aside.
As soon as you remove the Dutch baby from the oven, top with spiced pears, toasted pecans, and dollops of sour cream and heavy cream mixture. Finish with a sprinkle of powdered sugar and serve immediately with lemon wedges.