This sauce is a classic from central Tuscany and known as Salsa del Valdarno, a variation of acciugata that uses capers in place of garlic. It's most often used to dress a thick, t-bone steak that's grilled over charcoal but left bloody in the middle. It's also a wonderful partner to cauliflower, in any way. I often toss the sauce with steamed or roasted cauliflower as a side dish, without the bread—but serving it on toast (as a crostone), turns this into a quick, satisfying-yet-light meal. You can also try the sauce spooned over eggs—boiled and halved, fried, scrambled or poached. Tuscans like it on fried beef or veal, too. For a quick and thrifty lunch, my husband's nonna used to stir it into spaghetti. —Emiko
Break up or chop the cauliflower into small pieces. Cook in boiling water with a pinch of salt until just tender, about 10 minutes.
In the meantime, make the sauce by combining the olive oil and anchovies in a small saucepan and bringing to a bare simmer over low-medium heat. Stir gently to break up the anchovies, and add the capers (if you prefer, you can also chop these, I like to leave them whole, especially if they are very small capers). Remove from the heat once the anchovies have 'melted' down into a sauce, this happens fairly quickly, no more than 2 minutes total simmering.
Toast the bread (in a low oven, under a broiler, or on a grill pan) and set aside.
When the cauliflower is cooked, drain, and toss with the warm sauce. Pile the dressed cauliflower on the toasted bread and drizzle any extra sauce (especially the capers that tend to sit at the bottom of the pan) on top. Serve warm.