Preheat the oven to 325℉. Grease the bottom and sides of a 9-inch round (or springform) or 8-inch square baking pan with oil and line the bottom with parchment paper. Lightly grease top of parchment paper too.
In medium bowl, stir together the flour, baking powder, baking soda, and salt
In large bowl, whisk or vigorously stir the yogurt, oil, honey, rosemary, and zest until very well blended and creamy. Add the eggs, one at a time, mixing after each addition. The mixture should be thick and somewhat glossy.
With a rubber spatula, stir in the flour mixture in two additions, mixing after each until just combined.
Pour the batter into the prepared pan. Trim a 2-inch floret from the top of the remaining rosemary sprig and place in the center of the batter.
Place the pan in the oven and bake until golden on the top and a skewer inserted in the center comes out clean, 40-43 minutes.
Transfer to a rack and let cool for 10 minutes. Invert onto a serving plate or platter and cool completely. Peel away the parchment paper and serve.
