On a scale from one to ten, the décor at Raja's hovers somewhere around zero, meaning nothing -- but it's very, very clean. Nonetheless this hole-in-the-wall is a tiny treasure well worth preserving. Yet considering the now-you-see-them-now-you-don't pace at which downtown development is obliterating low-rent operations, one cannot help but worry about Raja's. And it's not just because the mom-and-pop luncheonette is unique, or because the Kandaswamy family, who hail from Tiruchchirapalli, south of Madras, run the county's only South Indian restaurant. But to find a better version of this fare anywhere south of Manhattan's Little India would be more difficult than trying to pronounce the owners' hometown. Although the steam-table curries provide fine instant gratification, the must-not-miss items are the $4.35 dosai (light, lacy, thin rice/dhal-batter cr?pes wrapped around buttery spiced potato filling); slightly thicker fried uttapam pancakes ($6.99), crisp-edged but springy in the middle and topped with chilies or onions; and fat steamed idli patties ($5.50) ideal for dipping in Raja's sweet chutneys and salty sambars. A glass of excellent mango lassi ($2.50) will make the twenty-minute wait for these custom-crafted snacks pass painlessly.