Keep berries frozen until needed. Mix eggs, milk, lemon juice, oil, and sugar until smooth. In a separate bowl, mix flour, baking powder, salt, and cinnamon. Add flour mixture to the wet ingredients, stirring only until moistened. Toss berries in additional flour and fold into batter. Spray a standard 12 cup muffin tray with nonstick cooking spray, and fill cups full of batter. Bake at 375 degrees, for 20-25 minutes. While warm, brush tops of muffins with softened butter and sprinkle tops evenly with turbinado sugar. Let stand in muffin pans for about 10 minutes, then transfer to a cooling rack, gently using a spoon to loosen muffin edges and scoop out muffins.