Position your oven rack in the middle and preheat to 350°F. While the oven heats, finely chop the strawberries into roughly ¼-inch pieces and slice the rhubarb into thin ¼-inch half-moons. Line your muffin pan with paper liners.
In a medium bowl, whisk together the almond flour, arrowroot, baking soda, salt, and ground cinnamon. Set the dry mixture aside.
In a separate bowl, whisk together the room-temperature eggs, honey, vanilla, and lemon juice until well combined and slightly frothy.
Pour the wet ingredient mixture into the bowl with the dry ingredient mixture, then gently stir until just combined.
Gently fold the chopped strawberries and sliced rhubarb into the batter using a spatula, being careful not to overwork the batter. Divide the batter evenly among the lined muffin cups, filling each about three-quarters full.
Sprinkle the roughly chopped almonds evenly over the top of each muffin, then sprinkle the coconut sugar over the almonds. Bake for 22–26 minutes until a toothpick inserted into the center comes out with a few moist crumbs.
Remove the muffin pan from the oven and let the muffins cool in the pan for about 5 minutes, then transfer them to a wire rack to cool completely.