Muffin batter. In a large mixing bowl, using your fingertips, press the lemon zest into the sugar. Whisk in the flour, baking powder, salt, and cornstarch.
In a medium mixing bowl, whisk together (use the whisk from the dry ingredients) the sour cream, eggs, melted butter, vanilla and lemon juice.
With a rubber spatula or spoon, mix the wet ingredients into the dry ingredients, just until there is barely any flour still visible. Do not overmix.
Cover and refrigerate at least a couple of hours or, preferably, overnight.
Strawberries. Spread the chopped strawberries onto a baking sheet lined with parchment paper so that none of the pieces are touching. Place in the freezer.
Crumbs. In blender, process the flour, confectioner's sugar, salt and freeze dried strawberries. Pour into a bowl. Add vanilla extract and melted butter. Stir with a fork until it resembles coarse crumbs. Cover and refrigerate until ready to use.
Preheat oven to 400° F.
Line 12 muffin tins with papers or grease the tins with butter or non-stick cooking spray. Spread approximately 1 Tablespoon of the cold muffin batter on the bottoms of each paper or muffin tin. Mix the frozen strawberries into the rest of the batter, being careful not to overmix. (If the strawberries are frozen onto each other, break them apart before adding them to the batter.) Fill the muffin tins with equal amounts of the cold batter. Sprinkle the tops with the crumbs.
Bake for 25-35 minutes, just until a toothpick inserted in the middle comes out clean. Bake time could vary depending on how juicy the strawberries are. Be sure to start checking them at the 25 minute mark.
Cool in pan on a wire rack.