To make the meatballs, mix together the grated onion, salt, red curry paste, and almond flour in a large bowl until well combined. Add the meat, stirring until all the ingredients are well incorporated, being careful not to overmix. Set aside.
In a large Dutch oven, heat the stock, 1 cup coconut milk, water, coconut aminos, ginger, garlic, lemongrass, and 1 tablespoon curry paste over medium high heat.
Scoop the meatball mixture into balls and add to the stock mixture. Cover, bring to a boil, then reduce to a simmer. Cook, covered, for 30-35 minutes or until the meatballs are cooked through and the broth is flavorful.
Meanwhile, prepare the rice noodles according to package instructions. Set aside.
At the end of the cook time, uncover and carefully remove the ginger, garlic cloves and lemon grass. Discard.
Add the remaining 1 cup coconut milk, 1 tablespoon fish sauce, spinach, and lime juice, stirring to combine. Taste and add remaining 1 tablespoon curry paste (or more) if a spicier soup is desired, stirring to combine.
Divide the cooked rice noodles between serving bowls. Ladle over the broth and meatballs. Garnish with additional lime juice, cilantro, mint, and chili or sweet chili sauce if desired.