Preheat oven to 400°F. Line a rimmed baking sheet with parchment paper or a silicone baking mat; lightly oil.
Remove the flesh from the baked sweet potatoes. Measure out 1 packed cup. (Reserve any remaining sweet potato for another use.) Place the potatoes in a large mixing bowl and mash well.
Add the almond meal, egg, cheese (if using), baking soda, dried Italian herbs, garlic, and sea salt. Mix until well-combined. The dough will be fairly damp. Bring the dough together into a ball. Transfer to the baking sheet. Oil your hands and press out into a 9- to 10-inch or slightly larger round that is about ½-inch thick.
Bake for 20-25 minutes.
Remove the crust from the oven and spread the pesto over the top. Top with the cheese, followed by the thinly sliced fennel and shallots, and halved grape tomatoes.
Bake for an additional 10-15 minutes, or until cheese is golden and bubbly and the crust is browned to your liking (we like ours pretty dark and crisp!). Remove from oven. Let cool for a few minutes, top with baby arugula, if using, and cut into wedges and serve.