Cook the spaghetti al dente. Besides (it really doesn`t take any longer) cut the tomatoes in half or quarter. Chop the garlic clove, parsley, anchovy fillets and capers in a blender, then pour in olive oil until the mixture becomes creamy (consistency like pesto). Mix everything briefly again with the mixer. Pour caper pesto over the tomatoes and then add the spaghetti. Mix everything well.