In a mixing bowl combine yeast, sweetener and warm water. Whisk well and let sit 5 minutes or until appearing foamy.
To the same bowl add flour, salt, baking powder and oil. Mix well. Cover with a damp cloth and let sit in a warm place for 1 hour or until doubled in size (it will be a rather wet batter, do not fret!).
Grease a 9"x13" pan and line with parchment paper (greasing helps the paper stick and hold shape).
Pour the risen batter into the center of the pan. Cover and let sit to rise for 30 minutes longer, or until the entire pan has filled with batter (see how-to photos in post for reference).
Preheat the oven to 450°F. Press a wet finger into the batter to make small indents throughout. Drizzle with olive oil and sprinkle with dried rosemary (if using). Bake for 17 minutes, or until the bread is firm and golden brown.
Let cool for 5-10 minutes before slicing. Optionally, sprinkle with a little coarse or flaked sea salt before serving. Enjoy!