What makes the first bearing of tomatoes have brown spots on them?

Sounds like you have a fungus. Apply a organic fungicide for tomatoes in the soil.

Generally brown spots are caused by water that is present on the fruit at the time when the sun hits it...in other words: sun burn marks. The best way to prevent that is to water the tomato plants when the plants are in the shaded part of the day...OR be very careful not to get water on the fruit or leaves when you water your plants.

The best way to avoid this problem if it is water spots is to water only at the soil level. I put down soaker hoses each season so I can just turn the water on at the house during dry spells rather than going up two very steep terraces to reach the garden. I go up there enough to care for the garden and it is nice to just step out the door and know I don't have to haul a hose all the way up and down all the time.