“ Catface” is a term for describing misshapen fruit with scars and holes on blossom end. Possible causes are cold weather with night temperatures 58 F or lower at flowering time, high nitrogen levels, and herbicide injury. The tomato varieties with very large fruits are more susceptible.
Cool and cloudy weather at blooming time can cause the tomato blossoms to stick to the developing fruit or each other. The resulting malformation, catfacing, may appear as puckering and scarring at the blossom end of the fruit. Although the cavities may penetrate deep into the fruit, the fruits can still be used after cutting away the damaged areas. For more information, refer to the vegetable publication HO-26W, Tomatoes (PDF 53K), from the Purdue University Cooperative Extension Service and Down the Garden Path #117 (PDF 172K)