Is there an IC that can be used to talk through UART port and get SPI port? For example, something that is opposite function of MAX3100.

No. A micro controller needs to be used in order to establish the SPI connection to communicate with the UART.  UART and SPI are fundamentally different in a way that there is no standard in translating one to the other. The command has to be defined by the interface, in this case SPI. Therefore, we cannot offer a device that can do opposite of MAX3100 because it is not just a simple matter in translating the UART to SPI or vice versa.  A micro controller will be the best solution for this.