Toast needs a topping that will stay put. Whole beans roll away; a completely smooth purée can feel a little flat. Mashing roughly half gives you both a creamy base and something to bite.
Drain a 400 g tin of cannellini beans, then warm them in a small pan with a tablespoon of olive oil, three tablespoons of water, and a finely grated garlic clove. Stir until hot, crushing some beans against the pan. Add lemon zest and black pepper. If the mixture turns stiff, loosen it with another spoonful of water.
Spoon over two substantial slices of toast. Chopped parsley and a little lemon juice belong on top, where their freshness remains noticeable. Ripe tomato slices are useful alongside, especially when the beans are rich and soft.
Eat while the toast still has crisp edges. Preparing the topping ahead works better than assembling the toast and letting it wait.