Various rodents could be getting to your ripening tomatoes. Squirrels, chipmunks, rats, voles, or mice could be causing this type of damage. Depending on the scale of your planting, you have several options. You could encircle the plants with hardware cloth (1/4 inch mesh) and place a lid of hardware cloth over the cylinder to completely exclude the pests from getting at to the plant. Or you could try to bag individual fruits as they are close to ripening.