• Bring all ingredients to room temperature. If using frozen berries, keep them in the freezer.
• Preheat oven to 350 degrees F. Grease and flour 1 large loaf pan or use 2 smaller disposable loaf pans (such as 8x4 inch).
• Combine the flour, baking powder, baking soda, salt, cornmeal and sugar in a large mixing bowl and whisk for about a minute, making sure everything is evenly distributed.
• Add the blackberries and raspberries to the flour mixture and carefully stir so that the berries are coated in dry mixture. If you are using frozen berries, do not add them yet, add at the end.
• In another mixing bowl, whisk the eggs lightly, then whisk in the yogurt, vanilla and lemon zest until smooth. Whisk in the melted butter, stirring just until blended and smooth.
• Combine the dry ingredients with the wet ingredients, and with a large heavy duty rubber scraper, fold everything together until well blended. If using frozen berries, toss the frozen berries in an extra tablespoon of flour and fold in last. Spoon and scrape the batter into the prepared loaf pan.
• Bake for about 45-60 minutes (loaf pan will influence the cook time -- my glass pan took about 70 minutes). Smaller loaves take about 60. Check mini loaf pans at 45 min. Internal temperature should be around 200F.
• Let cool on a rack for 20 minutes, then loosen sides with a knife and jiggle the strip of parchment paper. If the bread feels solid enough to lift, remove it from the pan and let cool on the rack. If it still feels delicate, let it cool completely in the pan.
• Slice the bread when it is completely cool.

Streusel Topping

• Mix together flour, sugars, pinch of cinnamon (if using) and salt (if using unsalted butter).
• Add the melted butter and stir until crumbly.