The top center of this 1-7 X4 Seed Onion dome is made of four (4) pairs of #1 & #7 mogharnas tiles. (See images.) The expanded version of this dome moves opposite pairs of domes pieces, each made up of dozens of the sixteen (16) muqarnas tile types. This results in four ‘ridged’ or ‘accordion’ folded connecting regions in the expanded tiers.
 
This expansion approach can be seen in the symmetry family of mogharnas domes which can be seen here.

Seed of Onion Dome
1-7 X4 Seed of Onion Dome

One (1) = 11.25°
1-7 X4 Seed

Seven (7) = 78.75°
1-7 X4 Seed

View from Above: Onion Dome with 1-7 X4 Seed
1-7 X4 Seed

Side View: Onion Dome Expanded with One Tier
1-7 X4 Seed

Onion Dome with Fourfold #1 & #7 Seed
15-15 X16 Seed

Onion Dome Expanded an Additional Tier
15-15 X16 Seed