In a small glass measuring cup add the 1/4 cup cold water. (A small bowl will also work). Add the 4 T unflavored gelatin and stir well. It will be clumpy, that is ok though. Let sit for about 5 minutes.
In the meantime, in a large glass measuring cup (I like my 8 cup Pyrex one-see link in Notes,) add the lemon juice and unrefined sugar or sweetener of choice. Add water up to the 5 cup line. Pour into a medium size pot and begin cooking on medium-low heat.
Add the hot water just off of boil, to the gelatin and stir well to dissolve. Keep stirring vigorously to get the little clumps dissolved.
Add the gelatin mixture into the pot and whisk very well and fast.
Continue cooking the mixture till the gelatin begins to dissolve and the mixture starts to thicken slightly. It should get just a little bit syrupy in texture and the gelatin should not be noticeable anymore. Then it is done cooking. This should take about 10-15 minutes. Note: you can use an immersion blender to blend for a brief 10 seconds to help get the last few stubborn clumps of gelatin dissolved.
Transfer into a medium-large serving bowl or plastic bowl with lid.
Place in the fridge for about an hour or two (will probably be closer to two hours at least) until it begins to set.
After 1-2 plus hours, jiggle the bowl. If it is getting pretty thick then it is time for the next step!
Remove from the fridge and take a knife through the jello making slices, about 1 inch apart. Turn the bowl and make slices the other way, as to make cubes.
Place back in the fridge while you make the whipped cream.
Beat the whipping cream, unrefined sugar and lemon flavoring or extract until stiff peaks form. I like to use a taller container/mixing bowl or liquid measuring cup for this step to prevent less mess.
Fold the whipped cream into the jello. If you are going to use a mold, now is the time to transfer it carefully. You want to do this step before the jello hardens too much or it won't be able to mold. Cover with plastic wrap and place in the fridge until ready to serve.