The first major development proposed for Block 57, a 20-story office and retail center in the ailing heart of downtown Salt Lake City, was unveiled Thursday before the Salt Lake Redevelopment Agency.

The Roger Boyer Co., a Salt Lake developer, wants to build a 350,000-square-foot, $40 million high-rise in the northwest corner of the block where the former J.C. Penney Co. Inc. building now stands.The City Council, which doubles as the Redevelopment Agency, was expected to meet Friday to consider providing a $4.3 million tax break, which Roger Boyer said his company must have to complete the project.

Boyer is also requesting a 31/2-year option to buy another slice of Block 57, as well as 390 costly parking stalls to be built by the city, before he breaks ground on the project.

Block 57 has been the center of private and public efforts to resuscitate the downtown area.