Prepare two silicon molds. I used molds with small heart shapes but feel free to use what you have—gummy bear molds, gummy worm molds, etc. all work great. If you don't have gummy molds, simply line a small to medium pan (smaller for thicker gummies and larger for thinner gummies) with parchment paper.
In a medium saucepan, whisk together the filtered water and agar agar powder. Set aside for 5 minutes to begin to dissolve the agar.
Meanwhile, add the strawberries and beet to a food processor. Process until a smooth purée forms, stopping to scrape down the sides as needed. Place a sieve or fine mesh colander over a bowl and run the purée through the strainer, using a spatula or spoon to press it through. You want to catch the smooth, fruity liquid in the bowl and separate out any fibrous fruit pieces and seeds.
Add the smooth fruit purée to the saucepan (the one with the agar mixture) along with the maple syrup and lemon juice, and whisk to incorporate. Heat over low heat, and bring the mixture to a rapid boil. Once the agar agar is fully dissolved and the mixture just begins to thicken, remove the pan from the heat.
Use a heat-safe eye dropper or spoon to fill the molds (or the prepared pan) with the gummy mixture. Transfer to the refrigerator and chill for as long as needed to set the gummies (e.g., about 5 minutes for smaller molds, longer for a pan).
Remove the gummies from the mold. Alternatively, if you're using a pan, lift the solidified gummy from the pan and slice into squares.
Store leftovers in an airtight container in the refrigerator for up to 1 week.