These savory muffins have a perfectly crisp crust and a cheesy, fluffy interior; they can also be downsized to mini muffins for a delicious hors d'oeuvre. Slideshow: Breakfast Muffin Recipes
Preheat the oven to 375° and position the rack in the lower third. Coat 6 jumbo muffin cups with nonstick baking spray. In a medium skillet, cook the pancetta over moderate heat, stirring occasionally, until browned but not crisp, about 7 minutes. Using a slotted spoon, transfer the pancetta to a paper towel–lined plate to drain.
In a large bowl, whisk the flour with the thyme, sugar, baking powder, baking soda, salt and orange zest. In another large bowl, beat the butter with the eggs until well combined. Fold in the dry ingredients and the buttermilk in 2 alternating additions, then fold in the cheese and pancetta.
Spoon the batter into the prepared muffin cups. Bake for 30 to 35 minutes, until golden on top and a toothpick inserted in the center of a muffin comes out clean. Let cool for 5 minutes, then transfer the muffins to a rack to cool slightly before serving.
The muffins can be stored in an airtight container overnight. Reheat for 5 minutes in a 375° oven before serving.