Start by gently sautéing the shallot in the butter, then adding the rice and let it sauté gently until it turns a milky white, then add a good splash of the wine.
When the wine evaporates, start adding the broth, ladleful by ladleful, and stirring from time to time. Once the rice has absorbed the broth from one ladle, add another ladleful of broth and keep stirring.
Repeat as needed. When the rice is half-cooked—after about 10 minutes—add half of the cherry purée in lieu of the broth, let the rice absorb it. Then continue with more broth until the rice is cooked al dente.
Meanwhile, gently simmer the other half of the cherry purée, letting it reduce until it thickens enough to coat a spoon.
When the rice is done, turn off the heat and add in the grated parmigiano-reggiano, along with another knob of butter if you like, stirring vigorously until the cheese has melted and the rice develops a nice creamy consistency. Your risotto should be quite loose. If not, add a bit more broth or water.