flowers on tomatoe plants just turning brown and no fruit coming

Tomato flowers are yellow, at least all the ones I've seen are, lack of fruit would indicate lack of pollenating insects. Either use a child's paint brush or a Q tip to pollenate the flowers.

With most modern varieties, just a tap on the back of the flower would do it--they are self-pollinating, and just need a shake to put the pollen where it belongs. If the nights have been below 15º C, The pollen may not be able to grow once in the right place, and you will need to use one of the many "tomato set" products, to fool the flowers into thinking that they have been pollinated. Allowing the plants to wilt between soakings will also kill the flowers before they have a chance to grow into fruit.