Preheat oven to 400 degrees F. In a small baking dish just large enough to hold 4 pear halves (an 8" square works well), place the butter and let it melt as the oven preheats. Halve the two pears. Slice the vanilla bean lengthwise and scrape out the seeds. When the butter is melted and the oven is preheated, pour maple syrup into the pan. Add in vanilla bean seeds and stir quickly. Place pear halves cut side down in the pan and return the pan to the oven.
Roast the pears at 400 degrees F until soft, about 25 to 30 minutes. Remove from oven and immediately take pear halves out. Tilt the pan to combine maple syrup with pear juice. Add in pecans and stir to coat. While still warm, scoop the center seeds out of the pears (I find it easier to do after they've been roasted) and place 1/4 cup yogurt in each. Top with maple syrup and pecans.