A combustor assembly for a gas turbine engine, the combustor assembly comprising: an inner liner, an outer liner, and a combustor dome together defining at least in part a combustion chamber having an annulus height, the combustor dome comprising a forward wall and defining an opening in the forward wall; and a fuel-air injector hardware assembly positioned at least partially within the opening of the combustor dome and comprising a swirler and a seal plate, the swirler being attached to the seal plate, the fuel-air injector hardware assembly further comprising a heat shield located at least partially within the combustion chamber for shielding at least a portion of the fuel-air injector hardware assembly, the heat shield defining an outer diameter, a ratio of the annulus height of the combustion chamber to the outer diameter of the heat shield being at least 1.3:1, wherein the combustor assembly defines a centerline, wherein the forward wall of the combustor dome defines a direction intersecting the centerline, and wherein the annulus height is defined between the inner liner and the outer liner in a direction parallel to the direction of the forward wall of the combustor dome; wherein the heat shield comprises a heat deflector lip, wherein the heat deflector lip of the heat shield defines a circular shape, and wherein the heat deflector lip defines the outer diameter; characterized in that: the seal plate defines a flange; and the heat shield comprises a radially outwardly extending mounting flange positioned upstream of the heat deflector lip; the combustor dome is formed of a ceramic matrix composite material; and the mounting flange is engaging a downstream side of the forward wall; the flange is positioned adjacent to a cold side of the combustor dome, wherein the seal plate is rotatably engaged with the heat shield and the attachment interface thus formed is a rotatable attachment interface formed of complementary threaded surfaces of the seal plate and the heat shield, and configured so that the two flanges (170, 172) are pressed towards each other against the combustor dome. an inner liner, an outer liner, and a combustor dome together defining at least in part a combustion chamber having an annulus height, the combustor dome comprising a forward wall and defining an opening in the forward wall; and a fuel-air injector hardware assembly positioned at least partially within the opening of the combustor dome and comprising a swirler and a seal plate, the swirler being attached to the seal plate, the fuel-air injector hardware assembly further comprising a heat shield located at least partially within the combustion chamber for shielding at least a portion of the fuel-air injector hardware assembly, the heat shield defining an outer diameter, a ratio of the annulus height of the combustion chamber to the outer diameter of the heat shield being at least 1.3:1, wherein the combustor assembly defines a centerline, wherein the forward wall of the combustor dome defines a direction intersecting the centerline, and wherein the annulus height is defined between the inner liner and the outer liner in a direction parallel to the direction of the forward wall of the combustor dome; wherein the heat shield comprises a heat deflector lip, wherein the heat deflector lip of the heat shield defines a circular shape, and wherein the heat deflector lip defines the outer diameter; characterized in that: the seal plate defines a flange; and the heat shield comprises a radially outwardly extending mounting flange positioned upstream of the heat deflector lip; the combustor dome is formed of a ceramic matrix composite material; and the mounting flange is engaging a downstream side of the forward wall; the flange is positioned adjacent to a cold side of the combustor dome, wherein the seal plate is rotatably engaged with the heat shield and the attachment interface thus formed is a rotatable attachment interface formed of complementary threaded surfaces of the seal plate and the heat shield, and configured so that the two flanges (170, 172) are pressed towards each other against the combustor dome. the seal plate defines a flange; and the heat shield comprises a radially outwardly extending mounting flange positioned upstream of the heat deflector lip; the combustor dome is formed of a ceramic matrix composite material; and the mounting flange is engaging a downstream side of the forward wall; the flange is positioned adjacent to a cold side of the combustor dome, wherein the seal plate is rotatably engaged with the heat shield and the attachment interface thus formed is a rotatable attachment interface formed of complementary threaded surfaces of the seal plate and the heat shield, and configured so that the two flanges (170, 172) are pressed towards each other against the combustor dome.