In a small pot, bring an inch of water to a boil. Add the peas and steam for 2 minutes; then drain and run under cold water. Set aside.
Trim the cauliflower florets, cutting away as much stem as possible. In 3 batches, break the florets into a food processor and pulse until the mixture resembles couscous. You can also grate the florets on the large holes of a cheese grater.
Heat the oil in a large skillet over medium-high heat. At the first wisp of smoke from the oil, add the onions and celery and stir to coat. Continue cooking, stirring frequently, until the onions are golden brown at the edges and have softened, about 8 minutes. Add the cauliflower, and stir to combine. Add 1 teaspoon salt, and continue to cook, stirring frequently, until the cauliflower has softened, 3 to 5 minutes. Stir in parsley and peas. Remove from heat. Season with salt and pepper to taste. Divide between two bowls and top with sliced cherry tomatoes.