In large saucepan melt butter over low heat. Add marshmallows and lemon extract and stir until almost melted. Leave a few marshmallows not all the way melted, you will want some lumps, this allows for the gooey pulls.
Remove the pot from heat and quickly stir in cereal and lemon zest until cereal is well coated.
Using buttered spatula or wax paper evenly press mixture into 8x8" baking pan. Cool then cut into 3x3 rows making 9 treats total, or 4x4 rows for 16 smaller treats.
Notes
Leftover treats will keep at room temperature for up to three days. Separate the bars with wax paper and store them in an airtight container.