Heat oil in a large saucepan over medium. Add shallots and cook, stirring often, until softened, about 5 minutes. Add garlic and cook, stirring, until softened and just beginning to turn golden around edges, about 3 minutes. Add tomato paste and cook, stirring, until slightly darkened in color and beginning to sizzle in fat, about 2 minutes. Add cherry tomatoes, miso, and 4 cups water. Bring to a simmer, stirring vigorously and mashing miso against side of pot to dissolve, and cook, stirring occasionally, until most of the tomatoes have burst open, (it’s okay to help them along with a spoon), about 5 minutes.