Line an 8x8-inch pan with parchment paper. Oil the paper and set aside.

Pour the cold water into the bowl of a stand mixer (or large bowl) and sprinkle the gelatin over top. Let stand for at least 5 minutes to hydrate.

Combine 2/3 cup water, monk fruit, allulose, and salt in a small pot. Bring to a boil and boil for 5 minutes to ensure all the sweetener is fully dissolved.

Turn on your stand mixer on its lowest speed (or use a handheld mixer). Slowly pour the boiling sweetener into the bowl as you mix. When all the sweetener is incorporated and the gelatin is fully melted, turn the mixer to high speed and beat until soft peaks and the mixture is only just warm to the touch, about 10 minutes. The mixture will be thick, white, and fluffy. Add the extract and color and beat until just incorporated.

Using a spatula, quickly transfer the beaten marshmallow into the prepared pan. You must work quickly as it will set on the whisk/beaters. Smooth the top and set aside to dry at room temperature for 4-6 hours, or until the top is no longer sticky to the touch.

Turn out of the pan, peel off paper and cut into 1-inch cubes. Dust the outside of the marshmallows with more powdered monk fruit, if desired. Allow to dry overnight before storing in an air-tight container.

If you want to make the optional coating, blend the freeze dried berries together with the powdered monk fruit. Pass through a fine mesh sieve, dusting the marshmallows as you go (this will remove the seeds). Toss the marshmallows as you do this to coat them evenly.