1. Preheat oven to 225°.
2. Beat first 3 ingredients at high speed with an electric mixer until foamy. Add sugar, 1 tablespoon at a time, beating until stiff peaks form and sugar dissolves. Add lemon extract and, if desired, food coloring; beat just until combined. (Stiff peaks will take on the consistency of marshmallow cream.)
3. Spoon mixture into a 1-gallon zip-top plastic bag. Shake mixture into 1 corner of bag; remove excess air, and twist to seal. Snip a small section from 1 corner of bag. Pipe 1 1/2-inch flattened circles onto parchment-lined baking sheets. Bake at 225° for 1 1/2 hours or until meringues look dry and no longer stick to paper. Turn off oven, and let meringues cool in oven 1 hour; remove and let cool completely on baking sheets on wire racks. Chill meringues in an airtight container before filling.
4. Gently spoon about 2 teaspoons sorbet on flat surface of 1 meringue, and top with another, working quickly. Wrap kisses on a platter in plastic wrap, and store in freezer until firm.