In a large bowl, combine the dry ingredients and mix with a whisk or fork until really well combined.
In a smaller bowl, combine the wet ingredients and whisk until smooth and very well combined; pour over the dry ingredients and mix well with a rubber spatula.
Transfer the dough to the prepared pan and spread as evenly as possible, then lightly press pecan halves across the top if desired.
Bake for 23-25 minutes, or until the top is nice and golden brown and a toothpick inserted in the center of the cake comes out clean.
Place the pan on a cooling rack and let the bars cool for at least 1 hour, then lift from pan and cut into 16 to 20 bars.
Keep the bars in an airtight container in a cool dry place for up to a week.