Preheat the oven to 300 degrees F. Line a baking sheet with parchment paper. Place the cherry tomatoes on the sheet and drizzle with olive oil. Sprinkle with sugar and salt and toss well. Roast for 1.5 to 2 hours, tossing every 30 minutes, until the tomatoes are super caramely and shriveled and sweet.
While the tomatoes are roasting, heat a skillet over low heat and add the butter. Once melted, stir in the onions with a pinch of salt and the brown sugar. Cook, stirring occasionally, until the onions get caramely and soft, about 35 to 40 minutes.
To make the garlic cream sauce, heat a saucepan over medium-low heat and add 1 1/2 cups of the cream and the butter. Stir in the garlic. In a shaker bottle (or in a bowl with a whisk), shake together the remaining 1/2 cup of cream and flour. It will create a thick slurry. Pour/scoop it into the cream mixture and stir well. Cook for 2 to 3 minutes, stirring often, until the cream sauce thickens.
Place the ricotta cheese in a fine mesh strainer and press it gently with a paper towel to release some of the liquid.
Begin to make your pizza! Spread the garlic cream sauce into the pizza, leaving a 1-inch border or so around edges. Top with the ricotta cheese. Add the caramelized onions and the cherry tomatoes on top. Bake for 20 to 25 minutes (or around 15 to 20 minutes if using the pizza stone) until the cheese is golden and bubbly and the crust is golden. Remove the pizza and let is cool for 10 to 15 minutes so the center cream sauce can set. Top with the fresh arugula and slice.