To make muffins: Preheat oven to 400 F. Lightly spray 12-cup muffin pan with nonstick cooking spray.
In large bowl, stir sorghum flour, cinnamon and baking soda.
In medium bowl, whisk buttermilk, brown sugar, egg whites, oil, lemon zest and vanilla. Stir into flour mixture until batter is just moistened and no flour is visible without overmixing. Spoon batter into muffin cups. Top each muffin with raspberries.
To make streusel: In small bowl, stir sorghum flour, brown sugar, oats, pecans, margarine and cinnamon to reach texture of coarse crumbs. Sprinkle over muffins, gently pushing into batter. Bake 16 minutes, or until wooden toothpick inserted in center comes out clean. The USDA recommends cooking egg dishes to 160 F.
Transfer pan to cooling rack. Let stand 5 minutes. Carefully transfer muffins to rack. Let cool completely, about 20 minutes.