Line a small rimmed baking sheet with parchment paper or greased aluminum foil.

Advertisement

Combine butter, condensed coconut milk, and lemon pudding mix in a heavy saucepan over medium heat. Cook, stirring continuously, until mixture has thickened, about 10 minutes. Remove from heat.

Beat in sweetener and lemon extract. Pour mixture onto the lined baking sheet and spread it out to an 1/4-inch thickness.

Refrigerate until fudge is set, about 1 hour. Lift fudge out of the baking sheet using the parchment paper and cut into 1-inch squares. Serve chilled.