You can search for highly expressed cell types (or tissues) here, starting from a gene of interest.
This page shows cell types (or tissues) with high expression for a selected gene. The results are displayed in a hierarchical manner, with cell types on the far left, followed by datasets in which that cell type was found to have high expression.
The number in the bracket after the cell type is the score given to that cell type for high expression. This score is higher if the mean value of all samples in that cell type is higher in the dataset. It is also higher if there are more datasets where the same cell type had high mean values.
Use tools > more options function to apply the calculation to tissue_of_origin field instead of cell_type.
Note that as the calculation requires looping through hundreds of datasets in the system, it may take up to a minute to return the results,