In a mortar and pestle (I've also done this with a knife!), bash together your garlic and basil with a fat pinch of salt to form a green paste.
Toss your basil-garlic paste with cucumber, tomato, and lots of olive oil, and lemon juice. Let it sit in the fridge for at least a few hours -- you can easily make this in the morning, go about your day, and pull it out in time for dinner.
Before serving, preheat your oven to 350° F. Tear your bread with your hands into uneven bits, about the same size as a one-inch cube. Let them be crazy. Toss with olive oil to coat. Toast them on a baking sheet in the oven for 10 to 15 minutes, stirring once or twice. You want the bread to be toasty on the outside but still a bit chewy on the inside. Let them cool.
Remove your salad from the fridge. Scoop out your vegetables and toss with croutons. Dress with the juice that's sitting at the bottom of your salad bowl. Save the rest for later; throwing away tomato juice is a cardinal sin of summer.